The "grave" on Trenzalore was the Doctor's entire timeline, from birth to death. Though history was changed and he didn't actually die on Trenzalore (so far, anyway), Clara still splintered all throughout his timeline.
Anything's possible, really. For all we know the Doctor will still eventually return to Trenzalore at some point in his life, and that's where he will die. He spent, what, 900 years there? Maybe he will eventually decide that that's where he wants to be buried.
Eh, I'm thinking that the timeline has changed, and Trenzalore isn't anything to The Doctor anymore. If that was the case, then Clara wouldn't splinter into the future. If nothing else, having Clara splinter into the future could theoretically justify bringing the character back at basically any time until either the show is cancelled or the actress dies of old age. The fact that they would have an in canon reason to bring Clara back for any Doctor at any time is too frightening to contemplate. Also, its a very depressing idea. Companions like Donna and Amy can basically never come back, but you can never get rid of Clara
