Straight from the horse's mouth: Sean Connery will not appear in the fourth Indiana Jones movie, as stated today on the official site for the film:
I get asked the question so often, I thought it best to make an announcement. I thought long and hard about it and if anything could have pulled me out of retirement it would have been an Indiana Jones film. I love working with Steven and George, and it goes without saying that it is an honor to have Harrison as my son. But in the end, retirement is just too damned much fun. I, do however, have one bit of advice for Junior: Demand that the critters be digital, the cliffs be low, and for goodness sake keep that whip by your side at all times in case you need to escape from the stunt coordinator! This is a remarkable cast, and I can only say, "Break a leg, everyone." I'll see you on May 22, 2008, at the theater!
His absence is disappointing, though not entirely surprising; if we think Harrison Ford is too old for the role, then the years have probably been even less kind on Mr. Connery (not that 76-year-olds can't act — just maybe not in a whip-toting action-adventure).
To be honest, I didn't even know until reading the above announcement that Mr. Connery had claimed to have retired. Too bad he couldn't have gone out on a higher note than The League of Extraordinary Gentlemen.
Moving on, confirmed cast members in Indiana Jones 4 are Harrison Ford, Shia LeBeouf, Cate Blanchett, Ray Winstone, and John Hurt. Of course, that's only because I haven't auditioned yet…