He has played the character across four films which span 27 years in time (from 81 to 08) and will span 39 years as of 2020. It is not "our projection of him on the character", it is that his characterization is what helped to make the character.
There have been others who have played in the role but outside of this forum how many really remember the YIJC? LC has River Phoenix but for what, 12 minutes of screentime? Ask any average movie fan who played Indiana Jones and I would bet 100 to 1 they would say Harrison Ford. Not George Hall or Doug Lee or anyone else.
It's a role that in the public mind due to the space of time has come to be associated with Harrison Ford. He is iconic in it. It is not like James Bond, which had a backbone of novels to support differing interpretations of the character, or like Batman which has the comics with alternative storylines and characters. The entire franchise is based around Harrison Ford's portrayal of the character. It's been that way for almost 40 years. More than a generation in time.
I do not think there is much hunger for Indy V; I think there's even less without Ford. Consider that the first post Connery Bond film flopped and he was only in that role for 5 years. Harrison Ford is as linked in the public to Indy as Sean Connery was for Bond in 1969. It will be uphill climb to sell a sixth Indy film without Harrison, and like with Bond, any reboot of Indy will have to make radical changes to stand on its own. There needs to be some hook to make a reboot work, and even then, I think they would rely on Harrison to cameo in a reboot to hedge their bets (like how Nimoy cameoed in the ST reboots)
I'm not saying Ford should be the only guy to play Indy, but I can't see a reboot coming out all that quickly after V, and I honestly can't even see V doing all that great because there's no demand, really, for it.