Wait 6 months for the 2016s come in and the 2015s will be on sale. I understand what you are going through, the wife loves all the bells and whistles and space of your Flagstaff but you are the one that has to worry about the maintenance and towing that behemoth. We camp with someone who has a Flagstaff and it has three slides, very spacious inside and has a 40"+ HDTV with home theater seats on one side, another couch, table with 4 chairs, island kitchen, the list goes on and on. Its a monster at 32'+ and a couple of feet taller than our AS. The 27 is going to feel tiny but the twins make it more spacious. Will you really enjoy the rear dinette with side couch compared with the couches in your Flagstaff? While the dinette is great for dining its not comfortable for relaxing and taking the table down every night to make a large lounge gets old. Even when its down its not that comfortable because the cushions aren't like the back rest and side arms of a proper couch. I put up with that because I like everything else about my AS floor plan and we don't want anything longer. We prefer to have the bedroom separated from the living area and that is impossible to find in a 25' SOB.
One thing you have to more concerned with is hail. Most hail won't hurt your Flagstaff like it would the Airstream.
You'e be better off selling your Flagstaff yourself and then deal with cash if you decide to proceed.
As with all RVs its a matter of compromise and what's important.