Formiddable Oldies

Hey guys,

I was just curious. With the current ability to upgrade and re-engine new aircraft, drop the airframe time down to zero during refurb’ etc. is it possible to make an old aircraft as potent as a modern 5th Gen fighter?
I’m kinda looking at what Romania did with the Fishbed/Lancer, they made an old out of date fighter into something capable of holding its own against a more modern fighter.

In say thirty years, will we be seeing aircraft like the Lancer still flying and will nations be able to upgrade old aircraft like the F-5 and MiG-21 to a standard where they can at least attempt to challenge an EF-2000 in the air (I give EF-2000 instead of F/A-22 for stealth reasons, I don’t think u can make a MiG-21 very stealthy except with perhaps advanced plasma)