Bayonetta 2 has the highest chance of going OOP. Everyone who wanted a copy already bought one, and all future buyers can go through the eShop.
I'd put a second vote in for Wii Sports Club. Copies are starting to dry up around here, and Best Buy's put it on clearance already...bad sign for a first party Nintendo game.
NSLU is already OOP but there are copies everywhere, plus it was bundled. I could see it at least holding its value.
One that I've been trying to get is the 360 version of PES 2015. It's OOS everywhere I look, but it could just be the holiday rush. Still, it could be OOP to push the new gen versions.
All of the low print run collector games like RCRDX and CoH2G will obviously be worth a lot.