Thinking about it further makes me realize that a dealership is probably justified in not guaranteeing incentives like that. Incentives have a known end date while a delivery date is out of their control. Price increases are much more infrequent and unknown.
A sincere advice to the OP. Educate yourself on how leases work. You cannot say I don't know the numbers behind the leases and still come out ahead. If you don't understand the numbers then you should not be leasing. Saying it with all sincerely.
When leasing, negotiate on the price first. Do not even tell the dealer you are looking to lease. Once the price is established, then have them give you both the lease and the purchase options.