that by any means possible I may attain the resurrection from the dead. (Philippians 3:11, ESV)"that by any means possible" does not mean that Paul is unsure what will bring him to the resurrection, it just means that Paul does not know how he will get there. Maybe he will attain the resurrection of the dead after he has died. Maybe he will be killed for his faith. But Paul doesn't know whether or not Christ will return before his own end. Maybe he will attain the resurrection of the dead when he is "taken up" like he talks about with the Thessalonian Christians.
What Paul is sure of is that he will make it to the end. He will endure. And what his end looks like is less important to Paul than the surety that he will keep at it.