To answer OP- Q7 deals will probably stay the same until end of December.
It’s already season of audi, and I’ve leased in that timeframe in ‘17 and ‘18, and they tend to keep everything about the same throughout November and December. You could find one dealer more willing to discount at some point rather than another, but it’s doubtful audi would make any changes to the program and support.
In regard to xc90 vs. Q7, I was in this boat last year.
IMO, the Q7, especially the v6 variant, is just a better vehicle. The only areas in which the xc90 beats the audi is exterior aesthetics (I think the xc90 in r design or inscription trim is one of the best looking SUVs on the road whereas the Q7 is bland) and the rear space (third row and cargo). Q7 is actually more spacious in second row; the Q7 second row is best in class. I also felt interior aesthetics, infotainment and overall fit & finish favored the Q7. I don’t love a 4 cyl on bigger SUVs, so that weighed heavily in my decision to choose the Q7, considering we are a family of 5.
All that said, the insane deals on xc90 probably make it a better lease value right now than a Q7.