Evenif they had started this summer, it would not be out until summer 2005. That's 16 years since the last crusade. Way too long.
And I think both Spielberg and Lucas are slipping, I can't see them making this movie in a way that will please us. There's no need to go into Lucas because its all be said before, but I'm in the club that thinks Spilberg lost his spark a long time ago as well. The only one of his movies I've liked since Jurassic park (which looking back is a highly flawed and problematic movie, FX aside) has been Catch me if you Can, and even it suffered the same problem that Minority report and AI did which was and ending that just would not end.
As for Darabont, I liked Shawshank, actually loved it. Green Mile not so much and the Majestic was okay. How good his Indy script was, we'll probably never know.
And Ford, don't get me started on him.
Personally I think we've all been spared a sequel that would almost certainly have embarrassed the franchise. Sure I would of lined up opening night to see it, but I can almost guarntee the Indy magic would be long gone, and instead we'd be treated to a lot jokes about Ford's age, a plethora of CGI, and a lot of santized PG violence, and PC values.