At this time it's prolly more cost-effective for the USAF to do high-low mix between F-22 and upgraded F-15's. At this point I seriously doubt the PLAAF J-11's are as advanced or battle-proven as the F-15 platform, which is being upgraded with AN/APG-63(v)3 AESA radar and JHMCS.
IMO the biggest strength of the USAF is in America's production capability. Despite all the hoopla about outsourcing manufacturing, the American defense industry can still output more advanced fighter planes than anyone else. So even if the PLAAF gains some measure of parity, the US can easily replace its losses while the PLAAF cannot.
The J-11/Su-27SK was a "stop gap" purchase, to catch up to other regional neighbors (Japan, Korea, Taiwan) and make PLAAF a more credible force. But compared to the latest western aircraft (F-15K/SG, F-16E/F), they're technically behind by quite a margin. We'll have to wait and see what the proposed upgrade (J-11B?) brings.