Ok, so I've got someone I'm going to go on a date with shortly, yet another person just suddenly expressed interest in me; I'm a one-girl guy, and I'm not going to go behind person1's back, and agree to meet person2, but at this point, I still have yet to date person1, and who knows, it may just not work out...

How can I suavely tell person2 that though I'm occupied at the moment and I hope she finds someone else, but make clear that if in the future I wasn't occupied, maybe we could get together?