+1 for this…
I’ve heard 21:9 is supported and also that to play 4K on triple screens would need 1080Ti’s in SLI. Sadly I can’t remember where… searching…
FOUND IT! Want Forza Motorsport 7 to look its very best? You’ll need a PC - The Verge
"ALAN HARTMAN, HEAD OF TURN 10 STUDIOS
“Oh, of course, of course [PC will be better]. I don’t know what that gap is come this winter when we ship the console. But there’ll be a gap. You can go spend however much you need to spend to get over it. Obviously, you can throw ten thousand plus dollars into your PC and build a killer rig, you can do multiscreen. That’s not what the console’s trying to be. The console is trying to be an entertainment device you just take into your living room, plug it in and you’re up and going. The PC commitment’s a different layer.
“The biggest difference from a game creator between the PC environment or the console environment is the efficiency we get out of the console hardware because it’s just a known platform. We know exactly how long it takes to transfer a texture from one place to another. We can map that out. We can make sure we have no gaps, no stalls. And we can just be super efficient in what we get. So we get a lot more out of the fixed console. There is no fixed PC right hardware config, right? So you have to build that adaptability into your code and that flexibility, and you just can’t assume things are going to work the same way.
“That actually ends up being a pretty big performance boost. And it’s where when I get the, you know, the teardowns, which we’ll have on Scorpio where they’ll take all the pieces out and try and do the off-the-shelf PC and say, ‘Well this is the PC that equals the Scorpio’ — it just isn’t. You’d need to go do that and add another 30 percent to your specs to make sure you’re going to get the performance we get.”
Well at least it mentions multiscreen and $10,000+ PC’s, sadly though, no specific mention of Crossfire/SLI… 
A second article on the same site mentions “older wheels” so there’s hope there. Especially as a pic part way down shows the TH8A shifter amongst wheels from Logitech, Thrustmaster, Fanatec that can be made out…
Looks like they might have listened to those denied triple screen & multi GPU support in Apex/FH3…
Anyhow it looks LIKELY that both will get support but not a direct statement giving concrete information. Personally as I’m only running 3 x 144Hz 1080P freesync monitors and not 4K, with FM7 running 4K @ 60fps on XBoneX with 6TFlops GPU power… My R9 290X’s are just as powerful an I got 2 of em…
Though Vega is coming and I’m planning to upgrade, 1 or 2 cards yet to be decided though ;D