It's official, and it ain't gonna be no reboot neither. This will be a proper fifth installment with Harrison Ford and Steven Spielberg.
I know many will be dubious, but I say bring it on. The oddly lethargic Crystal Skull is all the more reason to do this - the Ford era deserves a better send off. Age isn't an issue; Ford looked great in the new Star Wars and walked away from a freaking plane crash recently.
My suggestion? Keep Indy overseas for the whole movie a la Temple of Doom. And if they take The Godfather Part II approach where they do parallel narratives with a 30s era Indy (to smooth the transition to the inevitable recast), one hopes they favor the "Michael Corleone" plot line by a ratio of like 90/10.
Oh, and somehow I knew this would happen before another Indy video game showed up.