I think all these discussions about what the new movie should be boils down to the fact that people are fans of this movie series for different reasons.
Some folks enjoy the movies more for the action and the stunt sequences while others are a fan of the characters and stories themselves more than the crazy stunts.
I fall into the later category and because of that I think it's absolutely no problem at all for Indy to be an older man now. It's only natural that he ages like anybody. Of course he won't be as bouncy as his younger days but that is perfectly fine.
I'm excited about what the story will be, what sort of place we find Indy in now. Is he healthy? Is he sick? Is he with family or is he alone? Is he home or is he perhaps stranded somewhere? Where will his last(?) adventure take him?
There are so many possibilities!
I often see people here saying what the movie studios obviously are thinking or what they should do but the fact is nobody here knows that.
I don't think those people thought that Disney would actually announce a new movie with Ford and Spielberg on board, yet here we are.
I also don't think they would mention Ford in the announcement if he's only playing a smaller part in the movie, but of course that is just my interpretation. And I'm sure people will argue against it.