The successor to the PSP from Sony, the NGP, is now rumoured to have a new and official name.
The name just doesn't seem like a Playstation product. It has more of an overall Sony feel to it. If you look at the names Sony gives it's products, the Vita fits perfectly. If you're wondering, Vita means 'life' in Italian.
I personally don't like name of the new device because it doesn't really appeal to gamers. It is primarily a gaming device but it just seems like Sony are trying to brand it as something else. This is a risk as Sony could find a whole new audience along with the gamers or it could fail in both by gamers not buying in and the casual market not understanding the purpose of the Vita.
But in the end, it's safe to say that most gamers who get the device will just call it the PSP2 or when they try to be hip/cool around people who aren't gamers, they may refer to it as the Vita.