It's uncertain if there will ever be a reunion concert. Mike definately wants to do it. Bruce has tourned with Mike non-stop since 1979 and Dave still sees Mike as one of his best friends, so no doubt they'll be there too. But if Mike wants Brian and Al to be there, he'll have to do some serious ass kissing. Brian has said on a few occasions that he'll never go on stage with Mike again, but that doesn't say much cause he's known to change his mind all the time. I think Brian's in if Mike manages to get Brian's wife Melinda on his side. Melinda also acts as Brian's manager and minder (whenever someone asks Brian why he made a certain decision the answer's usually "Because my wife thought it was a good idea") and she's quite hesitant to let Brian get envolved with Mike again cause Brian has a very fragile personality while Mike can be very dominant. She just thinks Brian's better off as a solo artist. And Al, I'm sure he'd love to do a reunion concert but since Mike kicked him out of the band twelve years ago, he'll probably play hard to get.
If they'd do a reunion concert they would definately have to use a backing band. But which one? The old backing musicians (some of whom have toured with the band for up to 30 years)? Mike's band (the band that currently tours as "The Beach Boys")? Or Brian's band (the band that Paul McCartney once called "the best live band in the business")? That might be the biggest problem of all, to pick a backing band without stepping on too many egos.
If you'd ask me, this should be the line-up:
Vocals: Brian, Mike, Al, Dave, Bruce, Jeff Foskett (toured with The Beach Boys for 20 years and with Brian's current band for 10 years, often doubles Brian's vocals on stage and does the high notes that he can't reach anymore), Christian Love (Mike's son, currently tours with his dad and sounds an awful lot like Carl) and maybe Adam and/or Matt Jardine (Al's sons, toured with The Beach Boys when their dad was still in the group).
Guitars: Al, Dave and Jeff Foskett.
Bass: Ed Carter ('Steady Eddy", toured with The Beach Boys from the late 60s until the late 90s).
Drums: Dennis's son Carl B. Wilson plays drums (he's in a band with Carl's son Justyn), but I'm not familiar with their music so I don't know how good he is. If he can't do it, they should probably use Mike D'Amico (drummer of Brian's band) or John Cowsill (original member of The Cowsills, currently the drummer of Mike's Beach Boys and also a great singer)
Keyboards: since Brian's and Bruce's keyboards usually aren't plugged in on stage, they should get Darian Sahanaja (member and musical director of Brian's current band) and Scott Bennett (also from Brian's band, he can play pretty much every instrument).