Harrison Ford has been stated as saying he'd LOVE to do another Indy movie, but that things just have to fall into place. If they were smart, they'd have a 3-generation Jones movie: Sean Connery, Harrison Ford and Indy's son (x_name / actor.) God only knows he's seduced enough ladies along the way. I'd personally prefer the son of Karen Allen's character as they seemed to have the most history / best chemistry. The son could easily be in his mid-20's so the movie could avoid the annoying "my kid who is 12 is coming" crap.
Indy can't be part of all the action, but a possible son could. I mean, give the guy a break, he needs to carry on those awesome genes!