If your lease agreement tells that he will not sale the apartment and he can not let you out until this date then you have every right to appeal. Then you can say that he is breaking the lease agreement.

Please read the lease agreement carefully and then talk to the landlord and consult with your lawyer.

 Unfortunately, if your landlord chooses to sell your apartment building, all current leases become property of the new owner. BUT, this only means that you would start paying a new landlord. They can not make any changes to your lease (ie. raise your rent) or your tenancy until your current lease expires. I HIGHLY doubt there will be anything in the lease preventing the landlord from selling your place. Make sure you get a copy of your lease before your apartment sells.