Technically they've wanted to do 5 since before the original trio of films. The plan was always to do 5 movies, but Lucas, Spielberg, and Ford could never agree on a story for 4.
Wow, really? So is this likely a story they planned out a while ago then, meant to close out a 5 movie arc, or was 5 a sort of arbitrary number?
I'm not really sure what's left of Indiana Jones if you take out Ford's character and Spielberg's direction. The "archeologist hunting artifacts and dodging nazis and some supernatural stuff" is a really cheesy concept (on purpose) and so easy to do wrong.
Yeah, I agree with this. Without Ford/ Spielberg the concept is generic and not super enticing on its own. Not sure why people would prefer a movie that would surely just become mimicing the original style over one more attempt to recapture the magic.
Indiana Jones is one of the absolute least rebootable series to me. It's like Austin Powers without Mike Myers or something. It's got potential, but I'd prefer something new and preserving the legacy over trotting out the name for no reason.
Ghostbusters is totally rebootable though, the concept has a lot more unique potential and character independent iconography (Indy just has the whip and hat, which firmly belong to Ford, as Crystal Skull pointed out).
A reboot without Ford could just as easily be like The Goonies 2 or something, just without the Indy score and a less religious focus (which it already moved away from). So, whatever. If you're gonna do Indy 5, you mine as well use Indy while he's around.