I don't think people should be excited over the NX just because its a handheld, the DS and 3DS had excelent games but the hardware was deffenitely the worst part of them, especially, the cramps I have in my hands after long sessions.
PSVita is build on indies and third party support and a lot of people use the PS4 streaming- and monthly free games on them, I don't think a lot of PSVita owners will make the jump just because the NX is a handheld, to win PSVita owners over they need better online options, functionality then Nintendo has ever offered, more comfort in the way the handheld holds and... third party support.
So PSVita owners are in the same boat as everyone else, except for people who buy nintendo games JUST to play nintendo games, the waiting to see the console & games lineup boat.