Well, if he doesn't plan on getting a Vita anytime soon, then it makes sense to get it now. In a few years, it'll probably be discontinued and selling for too much online.
Well he can also purchase the game as a digital download. If he waits a few years down the line i'm pretty sure the price of the mem cards will be lower and other people will be making mem cards for the vita by then. Sony can't monopolize on the mem card situation.