I hate going into threads where Tommy has covered everything I want to say. Robert Altman was an auteur in his dedication to artistic vision and I hope that someone out there is willing to pick up the torch and run with it as successfully as the man himself did.
I think P.T. Anderson just might be the right man for the job, having worked with Robert Altman in the filming of A Prairie Home Companion. Plus, I think he shares Altman's keen eye for characters.
I regard Altman as one of the truly unique and beautiful directors with his rigid need to experimental, ironic, idiosyncratic, but most importantly - honest.
People really should watch the Altman films that Tommydski mentioned plus McCabe & Mrs. Miller, Tanner '88, Short Cuts and Cookie's Fortune.