Will Harrison Ford even be alive to film a 5th Indy installment?

He's looking really old as it is now, and while makeup can do wonders, it doesn't turn back time that much, especially when one's body is getting up in age too so they aren't able to do as much anymore as they used to. And despite the stupid move on Hollywood's part to wait 20+ yrs to film a sequel with him still as the main character, how many people are going to watch a little 100 yr old archaeologist still swinging across ravines with his bullwhip?