Travel space.
I've always been more of a fantasy guy, but there isn't much chance I'll ever go to some different reality where it's all magic, medieval, elves, and the like. So, the next best thing is full-on Sci-Fi. That is a possibility for the future. So long as we don't destroy ourselves before then. Whether or not that means Mass Effect/StarTrek level "Oh my god, there are freaking aliens. How amazing is that." Or Firefly "final frontier" type Sci-Fi. I would be all for it.
On a more realistic level, I'd like to go on an a Lord of the Rings-esque journey through some beautiful countryside. A group of friends and I plan on doing this one day, but who knows if it will ever come to fruition.
Wait, so your saying that you and you're friends plan to destroy the One Ring at Mt. Doom while be hunted by all manner of orcs, Nazgul and other monstrosities in service of Sauron?
...Dibs on being Gandalf.