Anyone can sue anyone else for any reason. That does not mean you will win. This country is chock full of frivilious lawsuits and it makes the lawyers rich. Your contract (if you have a written lease) is with your landlord, and has nothing to do with his contracts with the tax office or mortgage company. The Obama Administration enacted tenant protections some years ago that upholds leases in cases of foreclosure. Instead of looking to sue, why not look up this new law?