The Korean War prolonged Sabre and MiG-15 production

Would the F-86 Sabre and MiG-15 have remained in production as long without the Korean War?

Probably not. Wartime demand favored keeping established production running, while peacetime replacement could have moved sooner to newer aircraft.

The Korean War gave air forces a reason to keep established fighter production running. Without that pressure, rapid generational change would favor shifting factories toward newer designs. An aircraft already in production could keep supplying a war even when a successor offered advantages. The counterfactual therefore depends on production demands as well as the technical qualities of the F-86 Sabre and MiG-15.