Dave Mustaine already blew the lid on this earlier this month, but it is officially confirmed now. Motörhead, Volbeat, and Lacuna Coil will join Megadeth on the next run of Gigantour, scheduled to kick off in January. From Megadeth's official Twitter:
Megadeth is excited to re-launch Gigantour with metal heavyweights Motörhead, Volbeat and Lacuna Coil. Dates tentatively set for early 2012.
More bands will probably be announced in the coming months, but this looks like a good main-stage lineup.