tompicard said
specifically why wouldn’t it tell Paul’s fate?  

Well in fact the author knows that Paul is dead at the time of writing. See verse 20:25. The title is a later add-on, while the author intended to describe early Christianity through the life spans of Peter and Paul. And it ends when Paul is brought to silence in Rome, something the readers know, and by something awful the author does not want to make explicit.

tompicard said
so you wouldn’t find it odd if a history of the American Civil War ended with a very last sentence of 

“Abraham and Mary decided to enjoy a nice play at the Ford theater on the evening of April 4 1865”

As most readers know what happened and why make explicit something awful ?  

It is not comparable. Acts is an ancient document completely beyond the standards of modern historians. Acts is a very stylised “spin doctor” product intended to show the harmony of early Christianity as a joint result of Peter and Paul. If you think of Acts as a kind of history of early Christianity up to the time of writing, then it would be odd that it ends with a descrete note on the death of Paul, because that is what it does. Paul is Luke’s foremost hero, and Acts ends when Paul dies, and Luke prefers to give an optimistic account of the final two years of Paul’s life. I think most critical scholars subscribe to this latter view. 

tompicard said
Gavriel, thanks for your ideas. 

I have been searching more on this, did you know that it seems like Paul’s last two years mentioned in Acts, probably were NOT the final two years of his life.

Those were two years before Paul’s FIRST trial, which he was likely freed from, there was another second trial after which he was executed. 

see ** you do not have permission to see this link **

of course this is totally tangential to my original question, just post it, if you might be interested.  

If it is true that the two years mentioned at the end of Acts were not the final two years, I would have to claim that Luke didn’t know that, in order to uphold my argument.

It is beyond doubt that Acts was written and may be was repeatedly edited, starting from at least 85. This is based on the argument that Luke used Mark and other sources for the gospel of Luke. Since Mark must have been written at a time when it was not available to Paul (there are no allusions to it in his letters, and he shows no knowledge of the gospel material), and Acts quite some time after Luke’s gospel, it means that it is impossible that Luke wrote Acts when Paul was alive.

On the other hand there are many clashes between the chronology that can be inferred from Paul’s seven authentic letters (accepted by all scholars) and that of Acts. So it is absolutely possible that Luke missed something.  The article you refer to builds the argument on 2 Tim. iv. 16, a letter that is often held to be not written by Paul, by critical scholars. But it could have been written by someone who had knowledge about the final years of Paul.

Chris_Eyre said
I’ve seen it suggested that Acts may have been two volume to start with, and we’re missing the second volume (presumably because people decided that Paul’s death and whatever else was in there wasn’t part of the story they wanted to tell). I wonder if anyone can comment on how realistic this hypothesis is?  

May be it is more probable that Luke planned another volume, but never came to write it. That could explain why he quietly closes the “first” volume as Paul ends his life,  with only vague hints at it, and without any proper summing-up. At least to a modern reader.