I see his joy here as more proof. No, he doesn't have Rose and the adventure he'll never have, but that's it right there: He NEVER thought he'd truly be able to have Rose and that adventure, but now, through the miracle of a metacrisis thingie at the perfect time, a part of him DOES have that, and even more importantly, ROSE has him and a full, complete life with him. If he truly loves her unconditionally (as I believe he does), how can he NOT be happy about that after the initial, understandable, self-pitying grief has worn off?

That's such a lovely way of saying it and ties in so well with his happy glee. I really am hoping this episode *isn't* going to be completely emotionally draining. It'd be nice to have some fun! And the Doctor loloks like he's up for that.