When will Sonos update the app with a 3 band EQ? Bass-Mid-Treble?

You are asking "how long" about something which hasn't even been commented on by Sonos.  Optimism is great, but I wouldn't expect anything from Sonos on this issue, regardless of the time frame.

Oh well. You maybe right. Meanwhile I’ll keep hoping, and continue to ask. Or, sometime in the near future start buying components for a  system with greater control and flexibility. Sounds like Sonos is in the, if it’s not broke don’t fix it mode right now. And I don’t understand why they’re concentrating only on new speaker production only. Better speakers would seem to call for greater or enhanced E Q possibilities. Sonos just opened me up to the possibility of a great sounding surround system. Now I want to complete my quest for a great sound system experience.

Sonos has a long history of concentrating on stuff that sells more Sonos.

If you want a tweaker’s dream audio system there are many out there, just not from Sonos.

I went the opposite direction from you, my fancy audio system was given to a friend and I put in Sonos so I could just enjoy my music, not twiddling bits. Never going back.