Do you mean for playback in the specific room, or in grouped rooms?  

If USB-C is also used for power, will the power supply be external? That would not be very nice.

Just something plugged directly into the speaker and not grouped.  You cannot use a Five right now without a 75ms latency even if something is plugged directly into it and it’s not grouped/wireless.  I’m hoping this move to a USB-C input allows actual zero-latency (or close) operation.

There are many latency threads.

The image from the Verge shows two cords running to the rear of the right Era 100, so I don’t think the USB-C is power, it’s a designed input, an looks to be on the top.

https://duet-cdn.vox-cdn.com/thumbor/0x0:3000x1916/750x479/filters:focal(1500x958:1501x959):format(webp)/cdn.vox-cdn.com/uploads/chorus_asset/file/24444824/era100black.jpg

This twitter image shows the rear of the Era 100 and there is a clear USB-C above where it looks like the power cord is running in the Verge image.

https://pbs.twimg.com/media/FpcQWw6WcAI2yEu?format=jpg&name=4096x4096

There are some more shots of the product on twitter, and they show separate power ports.  The Era 100 has the  power connection underneath, like the Sonos One, while the Era 300 has the power port in the back.  The USB port, and a mic switch, are on the back of both products.  It also looks like they have thread bolt insert (whatever it’s called) on the bottom for mounting.

Edit:  The screenshots also show a bluetooth button on the back of both speakers.

While I understand why people would want to play audio input without delay for the specific room with input attached, I can see why that would be done for two reasons.  One is that you could then use  the aux input for TV input, which is not it’s designed use and probably not what Sonos prefers..  The second is that if used as designed for audio only, then the delay is not a concerned and playing grouped audio in sync is a bigger priority.    A switch to allow playback in both ways might be ideal, but again, syncing audio with TVs is not the design.  Maybe Sonos is at a point where they prefer flexibility even if it means customers used speakers in unintended ways.  The inclusion of bluetooth, assuming rumors are true,  on these speakers seems to lean that way, so who knows.

Verge talks of Sonos offering some dongle as extra. Just to be clear though, this will have to be a converter that takes the line level analog signal from a source device, and outputs that into what I think should be a digital signal that the USB  C line in on Sonos can read. Correct?

Yes, I believe that’s the case.   Here’s an older article about USB audio. I don’t know if the article is still valid, but it does appear that an analog/digital conversion needs to take place. The USB-C cable doesn’t carry an analog signal on it’s on.

I like the idea overall. Since so many sources are digital already these days, there shouldn’t be a need to convert to analog and then back to digital, a direction connection should be fine.  As I stated earlier, you should (maybe?) be able to connect an android or USB-C equiped iOS device directly to the speaker without any conversion, perhaps even having better audio than what analog RCA or 3.5 mm connection can handle.  It’s completely spuclation on my part, but there 

Also, if you do need to convert from an analog source to digital, you can use the dongle Sonos provides, or if you want to use some other converter device, you can.  If you don’t have a need for an wired input at all, then you aren’t spending money on something you don’t need.

One thing that’s interesting that I haven’t seen discussed yet is that this is the first Sonos speaker that isn’t has side firing speakers and is not not a soundbar, can be used in pairs.  Obviously, side firing covers side channels and broadens the soundstage on a single speaker.    When you have a pair of speakers, the outside side speakers can play the same role.  However, what do the inside side speakers do in this scenario?

I wondered the same thing. I wonder if when the 300s are set up as a stereo pair or used as surrounds, the inside side-firing drivers are disabled. And if it’s true that adding the 300s as surrounds will create a 7.1.4 setup with the Arc, disabling these inside drivers would make sense. Or it’s possible that the inside drivers will just play the same audio as the three (I think) front-facing drivers.

It does make some sense to disable the inside speakers as rears.  But then I keep looking at the promo image below, and the only speakers pointed directly at the main listening area are the inside  speakers. Seems like the inside speakers would do a better job of creating ‘side audio’ then the outside speakers, since there would be do wall bounce required.  However, also seems odd the the side audio would likely appear to be coming from behind the rear audio.  Maybe there is some DSP time delay to address that or something. 

edit:  Also, just a promo image.  If the actual recommended layout has  the rear speakers facing inward slightly, that changes things.

I felt the same about big fancy setups, spouse wanted something less intrusive than what I had.

After a while using the Sonos solution I find I’m very happy with the sound and the lack of complexity (when it is happy) is really nice. My knees really appreciate the lack of a rat’s nest of wires too.

That makes the 100 a very flexible solution for getting HiFi quality sound, even perhaps without the addition of a Sub Mini, for not a lot of money. SVC should make the geography limitations of voice control a non issue, and the line in will allow users that like an album art display to get that via device like an earlier generation Echo Show 5/8; earlier generation because the new ones have no line out jacks, although they may have USB audio out, I am not sure. And turntable fans are also catered to in a cheaper way than they are at this time.

Inside speakers will be a must for the common couch-against-wall setup. Look at a typical Klipsch surround speaker. Ideally you spill surround sound along the walls.

Really don’t know how to use the ERA 300 as surrounds since my couch is against the wall...

Since Sonos has not announced the Era speakers (if they exist), or the details, there’s no good way of knowing how they will work. 

I found this article about the Era 300 on the Sonos website.
 

https://blog-stage.sonos.com/en-us/guide-to-spatial-audio

This looks like an article in progress that will be posted later on the Sonos blog. The images are missing or blurred. It says the best use of the Era 300 is as rear surrounds with a sound bar at the front. They also provide some Amazon spatial audio tracks to try.

I stumbled upon this by googling “Amazon spatial audio on Sonos.”

Nice… but odd that outside folks would have access to their staging environment, I’d be guessing a misconfiguration ;)

Looks like the link is password protected now, so legit? 

I hope this doesn’t mean that the Era 300 can’t play atmos music on it’s own, without being bonded to an Arc or Beam (Gen2).  That would be rather disappointing.

The article clearly said (towards the bottom) you can use a single or pair of Era 300’s for Atmos music.

The link to article for the Sonos blog is requiring a password,  so the only information I have is what @dan8558 stated.

Okay Sonos it's March 1st start selling the damn thing already 

This is exactly why “leaks” don’t really help. Sonos will announce them when they’re ready, not when The Verge posts a rumor.

In this case, there’s some evidence that most of the “leak” may be accurate, but we really need to wait for Sonos to announce. 

There’s all sorts of reasons why they may not be ready to do so, too.