To give any sort of definitive answer would require first reading the lease and all of the writings/emails modifying the lease. I expect that you could make a strong case that your guarantee would apply only to the renewal of the original lease, and not to any expansion of the lease to new real estate or for the rent associated with that other real estate. I can't promise you that you would be able to entirely escape the lease.
Note, whatever else may be the case, you can terminate your status as cosigner in accord with the lease terms, such that you're off the hook in the event of a future renewal.

