Originally posted by: Death BOO Z
here's one theory:

first of all, there's a big time jump (about 10-15 years, bringing Naruto to the 4th's age at his death) and Naruto has a child of his own now, or at least a pregenant wife.

then there's something wrong with the kyubi (maybe the seal expires, or that Akatsuki releases him) and Naruto goes up against it, and ends up sealing the fox into his child, but this time, the child isn't shunned down and really is treated as a hero, and by that, he achives what was 'promised' to Naruto...
Poor Kyubi, always getting sealed up =P. But I'd have to agree that your theory of the ending is one of the good ones.