Nonsense Chalenge. In the Pacific theater combat would very rarely occur above 15k feet, even in 1945. Same on the Eastern Front, Africa, Mediterranean, Middle East and Atlantic... On the western front combat above 20k would normally only occur when strategic bombing was involved, and only with the USAAF. The RAF bombers flew at lower altitudes; the Lanc could barely get above 20k in a clean configuration. The only high-flying RAF bomber was the Mossie, and during daylight even they preferred to fly at treetop levels.
Faster and higher did indeed become the priority post-war; the advent of the atomic bomb combined with the long distance between the USA and USSR meant that strategic bombing became the most important part of the cold war (at least until ICBMs became dominant). Now however, the current generation of fighters are actually slower than the last, and the new designs coming into service, like the F-35, are even slower than many fighters from the 1950s and '60s... So no, it does not continue to this day.
