Looking forward to the year ahead, when we can finally start hearing talk of filming dates and maybe even casting rumors. (Although not at all excited for made up plot rumors.)
If Ford can play Indy at 77, he can play Indy at 79.
He turns 77 days before its scheduled to come out. He'll probably still be 76 at the film's premiere, and 75 when it starts filming.
And if they want him back for a a sixth too, they need to get that sucker ready to shoot back-to-back or or just slightly after 5 does, because I don't see it happening otherwise.