What did the apostles expect to happen right after Christ ascended?
They expected the seven years of wrath and vexation to come next on the prophetic agenda, then Christ's return to Jerusalem to set up His kingdom. Once the king ruled in Jerusalem, Israel would go into all the world to evangelize the Gentiles.
Les explains that as Christ was ascending, Peter and the eleven knew the Old Testament program. They understood that the next thing on the agenda was the coming in of the seven years of wrath and vexation. After that, they expected the return of Christ back to Jerusalem in order to set up His kingdom. When the kingdom would be set up and the king was ruling in Jerusalem, then the Jew could go into all the corners of the world and evangelize the Gentile. Les notes that this was to be Israel's role, and that many church-going believers do not comprehend this order. He connects this to Isaiah 42 and the Old Testament program, where God expected Israel to yet receive her king, the kingdom to be set up, and the Jew to go out into the nations of the world and evangelize the non-Jew.
The former treatise have I made, O Theophilus, of all that Jesus began both to do and teach,