What was the original ending?
Had to look around to find it, but this was the supposed script - and part of the original video exists on Reddit.
Quantum Leap Episode Scripts at Al's Place - Mirror Image
www.quantumleap-alsplace.com
So the deal is, Al, now back with Beth thanks to Sam leaping in the past to tell him he's alive, tells Beth that Sam is completely lost in time - Ziggy can't track him, and since his body isn't in the Institute Chamber, he's leaping as his actual self in their theory - and they believe he's now in the future, well past his own lifetime. Al wants to find him, and Beth encourages him to do so, not as a hologram, which he can't do since he's no longer tied to Sam, but as a leaper himself.
The idea for the sixth season is that episodes would be a mix of Al leaping into people to find Sam, and having his own adventures, while Sam would be willing himself into various points in the future to fix what it will become. Cool concept, but sadly never happened.