The context is unconfirmed right now but the cellphone footage uploaded three days ago on YouTube by user Mic00 looks recent and shows the musician joining a youth band lineup including horns, keys, guitar, bass and drums, for a run-through of his classic Continuum track Gravity.
These young musicians are seriously talented too but it looks like Mayer didn't bring his own gear a long as he's playing what looks to be an old Epiphone Les Paul through a small Roland combo. And he sounds like… John Mayer. Somehow making it sound like a Strat in the intro.
After Mayer generously gives the solo section over to the young guitarist in the band – who has our massive respect for keeping it together – the footage cuts to a jam with the horn section taking the lead.