Don't count AMD out yet, HBM2 is coming from them as well - plus they have stuff to counter the 1080, I'll just be really surprised if they beat it, or tbh match it.
Boiler, the 1080 is going to be a huge leap from even the 980ti, the 980 for certain, a single 1080 is supposedly faster (hard to say in what or how exactly) than 2 980 in sli but a leap. 1080ti - you may as well wait for the HBM2, in fact, IMO, the 1080ti will likely BE the HBM2 first card they release, but that's just a guess, but a measured one. It'll be well into 2017 most like.
It's personal pref, but I'm selling my 980sli equipped system for a cheap deal and moving to 1080sli in a new box, and will possibly sell all the vid cards in our other systems, 980ti sli and a Titan for 1080s as well.
1070 will be the card that really sells I'll bet, better than current Titan performance for 379 bucks, crazy. Too bad VR and SLI don't get along, as a 1070 sli system would be a very cost effective solution, it may in fact be the best bang/$ out there for guys running 4k or 1440p 144hz LCDs. I'm going to run a 34" 1440p 100hz panel with my 1080s, and my ultimate goal would be to run 3, or 3 27" Asus ROGs, as I have 2 already. Apparently they've done a pile of improvements on the nvidia surround stuff for 3 lcds, and I know a TON of Aces High players run 3 panels, HT even said so based off their hardware survey that the program does when you install/update/etc.
Good year for Aces High 3 to come out IMO, big time. Fantastic new hardware, and a lot of really capable current gen stuff that will have prices drop like a rock, and which will also have a massive buyers used market.