I don't post here very often, but I do lurk around for info and to see pics of customs. After reading this thread, I feel like sharing my thoughts on a possible Indy 5. Thanks in advance for reading these ramblings.
I'm 38 years old. My introduction to Indiana Jones was through the storybook to Raiders. Standing in the bookstore at 10 years old, I stared at the picture on the cover and thought...that's Han Solo! On Earth! After begging my Mom to drive me to the theater to see this movie I knew almost nothing about, I had my mind blown. That guy that made that Jaws movie that scared me out of swimming in pools (never mind the beach a few miles from my house) had made Han Solo even cooler! When Temple of Doom came out, I knew next to nothing about the plot. It was scarier than Raiders, but Indy was still Indy. By the time Last Crusade came out, I was working as a projectionist at an AMC theater, and all I knew about the movie was what I saw in the trailers. I loved it. Skipping ahead to KOTCS, the last advance info I learned was the title, when Shia Lebwhatever announced it on TV, and the fact that Marion returns. I conscientiously avoided any internet news, spoilers, interviews, set pics, everything. Never saw a trailer. I wanted to walk into the theater with as clean a slate as possible. I didn't even see the poster until I had already bought my ticket. Guess what. I loved the movie. It was no more unbelievable than Anything Indy had done before. Aliens 'n' Commies in the paranoid 50's? Perfect fit. The inter-dimensional travelers were worshipped as GODS. How is that any different from the religious aspect in the other movies? Just because YOU don't worship a particular Deity, it doesn't mean it's invalid. Indy 5 + Satanism in the 60's = my sick fantasy! And I don't worship anybody!
Anyway, to wrap up the rest of my opinions, there can be no other Indy than Harrison Ford. People have mentioned other action heroes such as James Bond, Batman, Superman, etc. who have had multiple actors portraying them to varying degrees of success. These characters existed in novels or comic books before they were hoisted onto the silver screen. They were pictured in reader's minds before they were immortalized in serials, TV shows, cartoons and feature films. Indy didn't have a face until Harrison Ford whipped the gun out of his treacherous guide's hand at the beginning of Raiders. Period. Young Indy doesn't count in my factoring. They should never recast him. I look forward to Indy 5, as long as he is dragged into a situation he can't turn away from. The Reluctant Hero can be any age.