Yup the main problem is to kill off the PSP and let the PSV actually dominate (like what 3DS struggled to do with its weak launch; the DS was still selling well). But yet another problem lies in the fact that PSP has loads of games which PSV obviously hasn't, and PSV isn't able to replicate it through proper bakward compatibility (like what the 3DS can do.)
And the thing about naysayers crying "DOOM". They are partially justified. Yes the 3DS seemed to fail and all seemed bleak back then, but the circumstances are different. The Vita, sadly, is "failing" at a much greater pace, even when circumstances are supposed to favour it very much.
Pretty nice launch lineup, same price as launch 3DSes, holiday season, 1 week before Christmas. All of these would normally equate to strong sales. But the Vita didn't get this. It sold for lower than 3DS's launch numbers, plus the pretty bad plummet (200k for 3DS, 72k for Vita for Week 2 after launch).
Even though the current picture shows a bad, bad situation for Vita, remember it is only Week 2 into the console's lifespan. There is a lot that Sony can do to flip the tables, like what the 3DS could.
But on another note, I do think that the Japan Vita's launch lineup would be more suited for a Western audience. Well, there isn't Monster Hunter or Dragon Quest or anything big (as viewed by the Japanese), and Uncharted doesn't really seem to be as big a thing as these traditional stronghold franchises there, so...
The only moment to deem Vita's fate would be after it launches in the West. If the Vita still blunders there, then I can safely guarantee that Sony's screwed. But I don't think that's the case. The launch lineup's clearly for a Western audience.
(And about Tales and FF X boosting Vita sales, I don't really agree with this. That Tales game (forgot the name) is a remake of a DS game, and FF X is only in early development stages, so the boost by Tales wouldn't really be huge, and FF would only come out a long time after, maybe a little too late to salvage the situation if anything bad happens in the nearer future.)
Even though I admit that I'm pro-Nintendo and rather anti-Sony (shit don't come after me), I believe that both the 3DS and the Vita need competition between each other in order to keep their own toes up against the smartphone tsunami. If either the 3DS or PSV flops, then nothing'll keep the companies on their toes to continue innovating (since they just outright reject the notion that smartphones are killing their platforms). Which means the whole handheld legacy on this planet's pretty much doomed. That'll be the real doom.
So doom for Vita? Hell no. Please.