Thanks for reminder, I really should buy it, but feels like this will be a PS+ freebie in the future...
The same thing can be said for any other game in the store though. The thing you have to ask yourself is it worth playing now (also owning) and not waiting. You could end up waiting 3, 6, or even 12 months before it gets offered, or it never does. By then, if it isn't offered you might completely forget about it or lose interest because of other games. It just comes down to if you really have an interest in playing it sooner rather than later, or at all.
You also have to consider we have no idea really what Sony will be offering with the Vita IGC anyway. It could end up being more like Big Sky Infinity and Chronovolt which are new games as they roll out, or even let them put more PSP games on it.
You still have a week to think about it anyway. It really comes down to the developer and if they want to put there game up on IGC, which we will never know until it actually happens.