John Mayer to tour with The Grateful Dead?

According to sources, a trek with the Grammy-winning singer and guitarist is being planned this autum.

The Grateful Dead reunion shows, five in total scheduled for June 27 and 28 in Santa Clara, Calif. and July 4-6 in Chicago, look to have a potential haul of $50 million just in ticket sales, according to Billboard's estimates, and could have sold six million more seats.

The staggering payday naturally leads to an even bigger question: will the "Core Four" surviving members of the Dead -- Bob Weir, 67; Phil Lesh, 75; Mickey Hart, 71; and Bill Kreutzmann, 68 -- take the show on the road, or will the Fare Thee Well concerts truly bid farewell?

Speaking to multiple sources, Billboard has learned that a fall tour featuring John Mayer is in the works. According to insiders, the trek is due to kick off in October, with the Grammy-winning singer and guitarist having already begun to jam in a rehearsal-like setting with select members of the group, chief among them Weir. Observers say he's ecstatic about the prospect. A rep for the band tells Billboard that it's "premature" to suggest any such outing is being planned.