Last week's news that Roc Nation CEO, Jay-Z would step in to headline Friday's All Points West Festival made waves, after the Beastie Boys dropped out of the lineup when Adam "MCA" Yauch announced that he was diagnosed with cancer. Now, since Hova will already be in the New York area for his first ever set-performance at a U.S. festival, can we also expect Mr. Carter to surprise fans with an "impromptu appearance" at Diesel Jeans' U: Music Tour at Webster Hall tonight?

The show's lineup includes The Roots, who collaborated on Hova's live album 'Jay-Z Unplugged,' as well as Drake, who will appear on the upcoming "BluePrint 3," giving him ample stage material for a performance with either artist. According to Blackbook magazine, a knowledgeable source claims that Jay will likely pop in to wrap up a set with The Roots. PR reps for tonight's event -- a follow-up to last years mega-concert, which featured M.I.A., Franz Ferdinand and a surprise performance from T.I. -- have not fully denied or confirmed this "surprise appearance," but some signs are pointing to a enthusiastic -- yes!

The speculation fueling this "possible appearance" scenario at tonight's shindig -- which Blackbook says might also include guest performances by Lykke Li and Solange Knowles -- is derived from Jay's zeal for surprise appearances. His June performance with Eminem at Activision's E3 party, in addition to his 2008 Rock The Bells performance with Nas and his drop-in on Kanye's Glow in the Dark Tour at MSG last summer, all give us high hopes for seeing the ROC in the building tonight.