To answer your question plainly, if your are in a lease, then yes you do still have to pay your landlord rent because the contract you signed requires you to do so. Just becuase your landlord broke his contract with the bank that loaned him money does not warrant your breaking your contract with him. With that said, if the lease guarantees you rights to the home which the owner has no ability of honoring it is not a valid contract. But keep in mind intention is different than ability, and you must be careful with this point. Regardless of this point a notice of default does not mean the owner is going to lose the home, and if they were to make payment in full, and you were to stop paying your rent, you would be the guilty party for not paying.

Moving on, this does present you an excellent opportunity to renegotiate the rent you are currently paying. If he is going to lose the home in foreclosure then he is not making payments and everything he is collecting from you is profit. Threatening nonpayment even with the full intention to pay and providing the notice of default to him (which you should do anyway - and you should not be opening other people's mail - it is a federal offense) as reason for the threat will probably result in an agreed lower lease amount, but make sure this will not come at the expense of a good reference when you look for your new home.

With all things considered you should definitely be able to negotiate a lower rental payment.