"We're planning a big one, man, a real big one," Gregg Allman tells Billboard.com. "We're trying to get all the people we know that we've played with to come and sit in and play. We've got confirmation on a bunch of 'em now ... You're gonna ask me who that is, right?"

Well, yeah...

"No, no, I can't tell you all the secrets," Allman says with a laugh. "Just think about all the people we've played with. We're shooting to get all of them. Of course, people are on tour, but not usually so much in March as they would be, say, in August."

As for other 40th anniversary plans, such as new compilation albums and archival projects, band representatives say that ideas are still in the discussion and planning stages and not ready to talk about yet -- although Allman notes that "we have enough of those, actually."

The Allmans' return to the Beacon in 2009 will also be big news because the group had to cancel a 15-show stint in May while Allman was treated for long-festering Hepatitis C. "I've never done that," the singer and keyboardist notes, "and had it not been a total emergency, I wouldn't have done it this time. But I just flat couldn't make it, man. They make you take this (medication), you might as well plan on staying home for half a year.

"It's hell, man. It's really hell, but it worked. I don't have all my strength back yet, but I'm getting totally back up on my feet again. And the shows have been wonderful."

The Allmans are currently on a stretch of late summer shows that wraps Oct. 11 in Atlanta. The group, whose last studio album was 2003's "Hittin' the Note," is playing a couple of new songs, and guitarist Warren Haynes says there's "probably about half an album done" and ready to record, hopefully in the new year.

"We haven't been able to think about much lately except getting through this year," Allman notes, "but, yeah, next year will be really nice to get into the studio. We're looking forward to that."