Did the twelve apostles realize that the prophetic program was ending?
No. Paul states that the twelve apostles thought they were still in their prophetic program and did not even realize it was falling away from them. By twenty-two years after Pentecost, Israel was rejecting it, and the prophetic program had begun to fall through the cracks.
Les explains that the twelve apostles did not realize the prophetic program was ending. Paul’s remark that they "seemed to be somewhat" was snide because twenty-two years after Pentecost the prophetic program was falling through the cracks as Israel rejected it. God had raised up Paul as the apostle of the Gentiles; while Israel went down, the Gentile assembly or church came up. Paul says the twelve thought they were still in their prophetic program, not realizing it was falling away from them. The context shows Peter, James, and John recognized Paul’s gospel to the uncircumcision, but their own apostleship remained to the circumcision.
But of these who seemed to be somewhat, (whatsoever they were, it maketh no matter to me: God accepteth no man’s person:) for they who seemed to be somewhat in conference added nothing to me: