I imagine the character will be recast eventually. I'm sure there's plenty of adventures he had in the 30s & 40s that we never saw.
It might take a while though, Disney seems to be hesitant to recast right now after Solo (which wasn't the fault of the recasting at all, but whatever). But I have to imagine that next June won't be the last we see of Indy.
As for the IP not being fit for a land, the theming wouldn't be super specific like it is with Star Wars, Harry Potter & Avatar. I feel that would give an Indy land a sense of timelessness. That's on top of the franchise being an enduring piece of American pop culture. Snow White & Peter Pan aren't particularly relevant, but I doubt anyone would complain about them getting more in the parks.