All sounds reasonable, but I fail to see the specific reason why you think 3-screen is not viable.
One can assemble a PC _NOW_ that would run 3x1920x1080 @60hz on full detail. If done properly, it would cost under a grand. If you factor in the PS4 volume and efficiencies of scale, even now the total cost of hardware to Sony to make this possible is gonna be under $6-700. Given that consoles are sold at a loss anyway, $500 price point seems totally feasible to me. And that's today. When PS4 comes out - it will be even cheaper to achieve. Personally, I'm not buying it w/o tripple screen support.
Re-read the post. In short, right now a single PS3 could run games on triple screens at 5760x1080p, with the necessary hardware (hdmis), firmware (configuring the graphics card to being capable to run such a high resolution) and software (games) changes, but the games will look and feel completely awful, horrid, unbelievably bad. That issue cannot be technically avoided with one non-upgradeable console.
All consoles have a limit, just like a PC that is not going to be upgraded. With that said try running .....crysis2 at 1080p max quality max filters. Lets say you get 120steady fps, now try running it at 5760x1080p: it won't be more than 60fps, and since you have a decent pc you know that with image quality (etc.) the sky is the limit.
That "console compromise" will always be there as long as consoles cannot be upgraded,
no matter if they cost $500 or $2000.
Now if there's a compromise, what aspect do you want to prioritize? Right now most games run at 30fps instead of 60: developers prefer the game looking the best they can (in one screen) even though that necessarily means less fps. Why? Because image quality in one screen is what sales in most cases, not a niche market of 3 screens players or 120fps on consoles.
edit: To be more concrete, lets say GT6 comes out for the PS4. What PD will want is making it run at (most probably) 1080p at 60fps, with the best image quality they can squeeze out of the PS4 though the PC developers version obviously runs better (more things on screen, better effects, resolution, higher quality models and textures, filters and whatnot). If the console is already maxed out how come can you expect it to run the same but now on 3 different screens, which is a lot higher resolution, at the same quality and without upgrading the hardware: it's impossible without drastically lowering image quality and all the rest (think of gt6 to gt5 quality), and that's something no one wants on consoles.
How do you get rid of that core issue? With 3 consoles, which is essentially upgrading the hardware, or the game not running at max quality if it is on a single screen, which is silly.
And as a bit of offtopic, tbh I wouldn't be confident on that the triple screen version (with 3 ps3s) runs at the same resolution as regular GT5 x3 with the same quality and with the same fps. Actually it is impossible with even the 2012 hardware as "linked" graphics cards = fps stutters, always.
In doubt, read again.