Other questions on the ending of Harry Potter and The Deathly Hallows!

There is an enchantment attached to Gryffindor's Sword. It always comes to the aid of a "true Gryffindor" who is bold and brave and daring. Neville showed all these qualities when he stood up to Voldemort. So it did not matter who had the sword, it will always come when needed.

If you recall, the sorting hat was there. Both the sword and the sorting hat were mentioned, i think in the chamber of secrets. The sword of gryffindor belongs to a "true gryffindor" and will show itself on the sorting hat if that person needs it. Neville showed courage even when he saw that Harry was 'killed', thus he was able to pull out the sword from the sorting hat.