There has been no news or an announcement from Sonos, but I imagine they are working on it since Apple Music is so widely used by Sonos customers.

I would imagine (based on little else) that if Sonos already supports lossless on other streamers, it’s more a matter of Apple providing the correct access point to tell Sonos where to point their players to. Apple is, unfortunately, known to be recalcitrant when dealing with third parties, and Sonos folks in particular. Look at how long it took them to fix the Android auth issue. They care (not terribly unusually) about people using their own ecosystem. Folks using things outside Apple products seem to receive less attention. 

It may be relevant to note here that Apple themselves are on record saying that Apple lossless and lossy sound the same to their engineers in a blind listening test. So there isn't anything audible you are losing today, or will gain if and when this is made available.