Sonos almost never disclose their future plans, when they have it’s caused more issues than it solved so i doubt they will do so again.  I can’t see the Line in being activated ever, the use case is tiny.

Nice thought, but that request only applies to a Sonos Five or Amp. I agree with @bockersjv. Also, I doubt Sonos will re-design the One and One SL for that purpose (line-in).

Although, I do have my wish for a new surround speaker with upward firing drivers to augment the Arc and Beam 2. Maybe called the One SL Plus . Again, JMWT. 

Very unlikely. The connection to the surrounds is time-critical, with minimal buffering to try and maintain lip-sync. Likewise the Line-In feed is also often time-critical, if end-to-end delay is to be minimised. Burdening the surrounds’ connection with a PCM Line-In stream would incur unnecessary additional risk.

Ok, thank you all.