For heaven's sake, ask your landlord! He's the only one who can tell you for sure what will happen and what you need to do, but I'd also find out on my own about legalities in your munipality or state and what your rights are. Look at your lease, bring it to a lawyer if necessary to check the fine print so you'll be ready whenever (if?) a change does take place.

if your lease is yearly they can't ask you to just move out untill your lease is up in most states. if your lease is month to month then the new owner can give you notice to as soon as they own the place. in most states you would have 30 to 45 days to move if you were month to month.