If this reboot is to work, it’s going to have to create a new argument, a new basis for comparison, while also remaining somewhat true to the original concept. No reboot is ever necessary, which means that any reboot has to justify its existence beyond just being a rehash of the same character with the same plots and the same villains.
Harrison Ford is probably too old to reasonably continue to occupy the role, and, for all its flaws, Kingdom of the Crystal Skull seemed to close off his part of the story more or less satisfactorily. We don’t really want to see Spielberg remake Indiana Jones and the Raiders of the Lost Ark, and we don’t really want to see anyone replace Harrison Ford. Not everyone is worthy to wear that famous hat.
We all expect a few things from an Indiana Jones reboot: that it provide us with the same thrills and adventure, the same good humor, with dashing heroes, and dastardly villains. More than anything though, we expect that it be worth the price of a ticket.