In the past when I have attached a line-in from an audio interface or iOS device out to a Sonos Play (10 years ago) I experienced a great deal of latency, more than I could tolerate for ‘live’ play.
The speaker didn’t behave like a normal speaker in that way as if the guts of the device was adding latency due to timing algorithm - not sure how but the latency was so bad I could only use it for listening alone.
I would consider buying the new speaker if the latency issue went away. Obviously, this is a consumer device but having the speaker have a dual purpose would help me decide to buy it.
joe