When Sheldon sings the final notes of "The Lion Sleeps Tonight," his mouth is not quite in sync with the words. Also, he moves his mouth away from the microphone just before the fade-out, but his voice can still be heard at the same volume.
James Earl Jones' name does not appear on Sheldon's list. However the names of Harrison Ford, Mark Hamill and Carie Fisher are listed. It is unlikely that Sheldon would leave off James only to consider meeting him in person later.
On his list of possible guests, Sheldon spelled Ian McKellen as "Ian McKellan". Since he has an eidetic memory, that would suggest he's never seen McKellen's name written down before (like in the credits for X-Men or Lord of the Rings)
On Sheldon's list for possible guests to his comic-con, he has Stan Lee, Leonard Nimoy, and Bill Nye. Sheldon has restraining orders from all three and since he is not one to break the law he never would consider asking any of them. He does, however, ask Leonard to contact them as he is not allowed to.