At least 7,000,000 users on a console with very little real exclusive (dominant) games? Perfect time for a comeback if you ask me. Even if some people have never played Halo I believe many more will give it a shot now.
This game doesn't make consoles, but it has proven that it play's a HUGE role in selling it.
However, I don't have any delusions of grandeur (yes, that is a reference) about Halo going back to the old days where it was the king. Is it something I wish for? Very much so. But times have changed, and I have my doubts. Always hopeful however.