The top speed range of these MiG 15-17 airplanes is in the transonic region, but, when they were first designed, the area rule was unknown. Even if owning a jet fighter is not exactly 'Maintaining pilot's performance', thus hard to obtain or license, the change looks not too complex to implement; curiosity, experimenting, is the force behind Aviation progress. Salut +
In a word, yes. But that sort of depends on the definition of "performance". The top speed would likely be effected only in a minor fashion, but the transonic acceleration would likely improve, as would the fuel economy.
It is worth pointing out that, largely by luck, many of these aircraft got some of the benefits of the area rule without specifically designing it. The location of the cockpit behind the intake required the fuselage to become larger in that area, especially when one considers the canopy, which ends just in front of the wing. And then the tail begins near the end of the wing and the fuselage begins to narrow behind the engine as well.
The shape of the fuselage MiG 15 and MiG 17 fighters resulted from the large diameter of the engine used, the Russian version of the Nene centrifugal turbojet. The "area rule" has more effect on the performance of aircraft in the transonic and supersonic speed range. A well known example is the F106 Delta Dart which had a higher maximum speed (Mach 2.3) than the preceding F102 Delta dagger (Mach 1.2) mainly as a result of the application of the area rule to the design of the F106 fuselage.