You can extend the lease and go month to month after the lease end end date, which would buy you time until the Tesla arrives.
As for trading it into a company other than the dealer you bought from...it depends on who is your leasing company. Many are getting smart to the upside-down market and no longer allow you to trade in a lease to another seller since the car is worth more than the residual price agreed on when you started the lease. You must close out the lease yourself by buying it from the dealer you got it from, and they can add on fees as well. They rerally want you to just give the car back so they can make some money. Nissan forces you to only buy back from the dealer, so does Kia. However, GM (Ally) and Mazda allow 3rd party to buy your vehicle, for example (they used to last year, anyways).