If China were allowed to subjugate Taiwan, the PLA would probably occupy the island or at least enjoy extensive use of its facilities, not to mention any Taiwan weaponry that survives the cross-strait conflict (the island has hundreds of F-16s and Mirage2000fighter jets).
Foreign fighter planes are coming along--the Russian SU-35, the French Mirage2000 and the Swedish Gripen, among others--that will match our current crop of fighters.