With the new SMP for 3monitor gaming I'm considering switching over to the 1080s. With nvidia not fully supporting 3way SLI, would 2 1080s be enough horsepower to drive 3-1440p monitors @144hz (7680x1440) resolution at high/ultra specs?

Yup the benchmarks I've been seeing at 4K for a single 1080 are around 30-ish to just under 60fps for 1 card.   Depends completely on what game though.    I don't think Nvidia send any review sites 2 cards, so we'll need to wait a bit for SLI reviews.
I'm aiming to try to get solid 120-144Hz @ 1440p with max settings.   Preferred 4xMSAA or similar real AA.    I really hate FXAA or most post-processed AA that most games seem to be doing now.    So I'm looking at 1080 SLI too..  eager to see some benches!

Most likely a definite no no, hopefully 1080ti or titan sli will do it though.  I run some 7680x1440P on say the division and I get 40ish fps at medium high settings.  Battlefront  was around 45 fps I think, highish ultra.  Battlefield 4 is around 45 highish ultra.  Witcher 3 at that resolution on ultra with no hairworks was around 30 fps I think.  But that doesn't take into account minimums either.   
 
I've resorted to running at 5120x1440P, which is actually a little better cause the warping is nowhere near as bad with only half of each of my outer 2 monitors, and at that res I get a lot of my games closer to ultra and at least in the 50's.  I'd like to run with smp and full surround but don't think it's possible yet except for racing and flying games, I can hit around 60 fps ultra at 7680x1440P, which is what I mostly use it for anyways.       

Well i don't get it .I'm running 7680 by 1440 surroud at 144hz on 4way sli titan blacks , with cpu at 4.6 and ram at 3000. and in a 10 man rad in warcraft  i'm doing between 110 to 125 fps with settings all maxed out. Gsyn  and alis off . You don't need them on at that monitor rate ,or should i say i dont need them on. And with them off it make for a  large jump up in your fps. Like in battman with them on i got  (benchmark low 23  and  hi was 98 but av was only 45)but trun them off and just as clean and prefick asfar as i could see (benchmark said low was 53 hi was 170 ave was 110).  most of  the games i have tried , seem to work out that way, but i dont play some of the ones you all are talking about. But if i drop back to just one monitor at 2560 by 1440 at 144 gsyn and  alis both off i run about 200 fps. at that high of fps u dont need them . So my point is if the new card is as good as they say it should do what you want. but for me ,other than the clock speed i have not seen anything that would make me upgrade mine yet. i will wate till they have a 4/way hb bridge and 4/way titan cards . thin i buy. anything less is a waste  of money to me .

I have the same res specs as well with SLI 970s and 2D Surround is not always playable with Supersampling or AA enabled since there is not enough VRAM.  Most games I can max out all the other settings, but FPS usually stays around 30FPS.
 
Having said that, I heard part of the problem is that Previous Versions to Pascal required 1 Card per Monitor (3-Way SLI) in order to maximize the full potential of 2D Surround due to the nature of the order frames were rendered.  Pascal architecture will allow efficient frame rendering even with 1 card.  So that alone may add FPS.  
 
If I had to guess, SLI 1080s on 7680x1440 with Ultra settings and Supersampling/AA off, would hit in the 60-70FPS range.  Really think our resolutions will require at least 12GB VRAM to really be able to be fully worth while. And Faster RAM will be needed, GDDR5 and the GDDR5X dont appear to be fast enough.