In the west I'm dreadfully afraid of Vita's shot at success. Japan I'm a bit more confident about, but I'm still uncertain there.
I don't think it really can replicate the system sales in either country. Indeed, will the PS3 even surpass the PSP in lifetime hardware sales, worldwide? As of now it's apparently 55 million vs 71 million (going by Wikipedia). I guess it will, but it won't be by much, probably, depending on if the PS4 launches in 2013 or 2014.
The only way I think it does really well in Japan is if somehow MH isn't a big hit on the 3DS, leading Capcom to put it on the Vita. And in the West, well, if you are a fan of PS3 franchises, I guess it's great. But the PS3 is in 3rd place by a wide margin.
I think Sony could have taken two different routes. One by sort of copying iOS, coming up with a Sony ecosystem of movies, games, music, books, etc, all accessible on all their devices (where applicable). Sort of like Amazon has done with the Kindle Fire. Have the Vita Handheld being the equivalent of the iPod Touch, a 7" tablet competing with the Fire/Nook Color, and then a Sony Vita phone.
Since they own a great deal of media IP themselves, they would have an advantage over Amazon or Apple, at least in theory.
But of course, this route was impossible since Sony never ever cooperates with itself unless it absolutely has to.
The other route, which they took, was by going for a dedicated gaming handheld. Which might work, if they put out AAA games for it and secured exclusives from big name publishers. But of course, they would distract them from the PS3 and presumably PS4, so basically just repeated what they did with the PSP, only using PS3 spinoffs rather than original or rebooted IP. But as I said, the PS3 is the 3rd place console, so that strategy was perhaps misplaced...