Taylor Swift and Travis Kelce 's wedding celebration is shaping up to be a once-in-a-lifetime concert ... with some A-list guests reportedly scheduled to jump on the stage for some performances. Taylor's longtime pals Stevie Nicks and Tim McGraw are slated to sing some songs at New York City's Madison Square Garden, where Tay and Travis will be saying their "I do's" next weekend, Page Six reports. Meanwhile, sources tell TMZ Paul McCartney 's name has also been mentioned as a third potential