manicm:I think Sonos is targeting a certain buyer for whom hi-res is not a high priority.
I don't know if "targetting" is quite the right word, when Sonos designed their original components 24-bit music really didn't exist (in any meaningful sense), even when the ZP90/120 was introduced (which is what, 3 years ago?), it still wasn't really much of an option for >99% of users.
Now they're in a situation where the current hardware doesn't support it (the output is actually 24-bits wide, however 8 of those bits are used for volume control) but they know there's some demand there, however the ethos has always been "all your music everywhere", so whilst they could introduce a 24-bit player that'll leave them in a situation where it'll be more like "all your music in one play and the rest everywhere" and that will lead to complaints (it will, check the Sonos forums now if you don't believe me), which they'll try to avoid if possible. If they don't support 24-bit though, they will start to lose sales.
I don't really know how they get around that though, it must be a real headache for them at the moment.