I admit to being a bit conflicted on this. I have no problem with an older Indy, and I think Ford did a great job in KOTCS, though I do agree that they waited a bit too long to make it happen. The only way it could really work now is if they film it in the same vein as the conveyor belt fight in ToD, with Ford just doing close-ups and having a stuntman do the rest. I doubt Ford (and even many of us) would want a film of someone else basically doing all of his work for him. The only other option is to bring someone younger along but then we run into the same problem, with Indy sitting by and watching someone else take out the villains. An entire movie of that would get dull quickly.
I too fear that Ford's time is up and Disney seems to be in no hurry to get this project off the ground. Nothing about this feels good right now.