Last I heard he was. I know he almost pulled out because the studio bosses wouldn't let him cast Jason Lee as the lead but he was enticed back by the worry that, if he didn't do it, someone else would & they'd probably do it badly.
Last I heard was that after the critical and box office trouncing that "Jersey Girl" (rather undeservedly, I felt) got, he had lost his bottle and didn't want to be in charge of a multi-million dollar summer blockbuster. He's still providing the script, though.