Create your own supergroup...

I'd go with:

Jon Anderson - Vocals (There's no better prog singer)
Steve Hackett - Guitar ('nuff said)
Bill Bruford - Drums (Skinsman supreme and his electronic drum kit could add different textures and colours to the sound)
Tony Levin - Bass and stick (Again a different sound where possible)
Tom Brislin and Guy LeBlanc - Twin Keyboards (Twin keys for an amazing sound)

The band could be called Genecamelyesis for obvious reasons