It's pretty stupid to let a franchise which has tons of potential die off with an actor. Indy can be more than Harrison. And when he's gone, or when he cannot play it anymore, it should be. With newer writers, newer directors. Just stick to the groundwork for the character that was developed between 1978 and 1981 and get an actor who is pretty much a Cary Grant/Clark Gable/Humphrey Bogart clone like Harrison was and it'd work. It's not a role where the actor was some amazing method actor. It's not like remaking The Godfather, where Brando created the character (the look, the way he spoke, etc). Indy isn't about an actor or even the character in terms of backstory or whatever. Indiana Jones has parameters but it's more about a vicarious existence than a character, actor based piece. It could work fine without Harrison.