Why is Peter never mentioned again after Acts 11?
Peter is not mentioned again after Acts 11 because Israel was falling out of the things God had promised, the Gentiles were making an ascendancy, and the Body of Christ was coming on the scene. The transitional book of Acts shifts focus to the Gentiles and the Body of Christ.
Les explains that after the stoning of Stephen, the next major event is the conversion of Saul of Tarsus. Peter goes to the house of Cornelius in Acts 10, and Acts 11 has a little mention of Peter. From then until the end of the book of Acts, Peter is never mentioned again. Les says this happens because Israel is now falling out of all the things God had been promising, the Gentiles make an ascendancy, and here comes the Body of Christ. He also points out that Acts has a transitional aspect.