The purpose of offering Silva a 10 fight contract is to make sure he's locked up with the UFC when he retires and can't fight for any other promotion without the UFC's OK. It's business tactic and a smart one of the UFC's part. He's not fighting 10 more times.
I personally think once Silva decides to retire he should be able to do whatever he wants. I think that's obviously in his best interest, but the UFC will NOT let that happen.