Sorry, forgot about what rfactor did, but for the most part it won't be messed with as most games calculate a single very wide FOV instead of multiple FOV's. And I doubt we'll see such madness again anytime soon.
Guess we'll have to forget about IL2:1946, Black Shark and iRacing too, as this would be just madness to properly support 3 screens properly !
Sure most companys won't support the wider screen because they feel they have no target audience, but then not so long ago you had to hack a game to be able to play it on 3, now support is being built in as default more widely.
I'm sure there a other ways to fix the fisheye, as I dont like the 3 viewport mode, as my monitors aren't facing 90 degree angles to each other (22 deg would be more desirable imho) so isnt practical for most.
We know that the further from the centre the worse it is, and can anticipate these numbers, so could apply a software (ingame or overlay ala softTH) compression to compensate for this, sqeezing the display the further out you go.
This would probably leave some black space on the sides of the monitors, but small price to pay for a clean view.
Maybe if you have 1. 16:10 monitor and 2. 5:4 on the sides you could connect the primary to the centre DVI and run the 5:4's by a DVI to vga adapter on your widescreen resolution to compress the outer monitors display, to offset the distortion.
Obviously normal stuff like the desktop would be all screwed up, but I'm thinking outside the box to suggest possible other ways to address the issue.
I don't think this is impossible to fix, and its more a matter of time before its supported properly or some kind of hack is found.