a Technical Service Bulletin (TSB) usually has a limitation on warranty repair coverage. The TSB will normally state what the warranty limitations are. Whether or not the dealer would cover the repair depends on a lot of variables; Dealer participation, service history, and product commitment. Usually when a TSB is performed outside of the warranty limitations, is due to a Goodwill gesture approved by the dealer and Ford.
I hope this helped a little. I work for a dealership as a Service Advisor. I would usually recommend that we diagnose the concern first, and not be quick to think a TSB would cure our concern.