I have a playbase and two ONEs as my surround. While the sound is great, I think it could still be improved upon. I would like a 'wider' soundstage. I would also like Atmos, so I can hear the overhead effects.
If sonos were able to provide a software update that would recognize additional speakers, I would buy them. A suggestion, instead of having 'upward' firing speakers, would be to have an extra set of Ones placed up high on the walls near the ceiling, or maybe sonos could come out with some flatter, ceiling discs that could be the upper speaker. I don't imagine the ceiling speakers would need to be super powerful to provide the sound.
imagine a helicopter flying overhead. You hear it coming from overhead, but you would "feel" the boom boom boom at the ground level, which could be provided by the bass in the other speakers.
Also, the software update could possibly allow you to use the playbase as only a center channel and recognize additional ONEs at the far left and right. Perhaps these could also have upward firing speakers?