Indy 5 will be the first installment of the series under Disney's helm, and I think they'll be looking to please their target audience.
Would it make sense for them to move the Indiana Jones franchise further and further away from its all-action roots? I doubt it.
Look at what they did with Star Wars: it was totally back to the roots, and it paid off in spades.
Indy 5 gives them a unique opportunity to kill two birds with one stone.
Give Ford a worthy sendoff to appease hard core fans, and introduce a younger actor in all-action flashback scenes to lay the foundations for future prequels.
I'd be very surprised if they didn't take it.