Most of your questions have been covered in the Announcements thread.  Summary:

You will still be able to administrate your system.

You will still be able to add new products.

You will still be able to re-add old products.

Controller details have not been stated yet.

Thanks, since it’s over a thousand messages there it’s great to have these details collected separately like this. This sounds a lot like the kind of legacy options some of us wished for when the CR100 was EOL:ed.

Yes, it does.  Ironic, isn’t it?  

Truly ironic.

So re-add old products means I can reset those I have but not add others not previously in my system found 2nd hand?

Don’t know about that.  Seems they are being purposefully scant on details until May. 

OK, I see. We’ll have to wait.

Except it’s not accurate! Sonos requires that the same software on all devices in a network.
 

If you bought a new device on a higher version of software you would not be able to connect it to a legacy that work.
 

That’s why they’ve said that mixed systems of you and old components cannot be upgraded after may. 

Except it is accurate.  @Ryan S, can you please testify to the accuracy?

What they have said is split your networks so you have 2 Sonos setups. Old and new. 
 

No details on how that will work. How phone controllers etc will manage which have / automatically get updated.  

You can either do that, or leave them all as a legacy system.  Legacy systems will not get the regular upgrades, but you will be able to add new products. 

Now as I have requested confirmation from @Ryan S, why don’t we wait until he clarifies before escalating this disagreement, OK? 

Hey guys,  you will be able to add players to a legacy system but we haven’t shared all the details around how this will work yet. 

Sonos shuld also consider re-adding the CR100 to the legacy version. There are a lot of CR100 out there and a lot of us users wished for a legacy path in 2018. Now it’s here. Now you can fix that!

I used to be a CR-100 user but I took the $100 rebate to recycle mine so I’m good with that.

Sonos should sell the legacy IP to a support company or make it open source. They have no commercial interest in it, but I would happily subscribe to a support contract to sustain my legacy kit. How about it Sonos?

Yes this!