Anyone know why they never made a third movie? Answered

IMDB still shows it as a possibility. Who knows if, or when, it'll get made.

Conflicting schedules and a very difficult script to write from what I've read is the reason for the delay.

Abigail took all of his property and he didn't have the taxi fare to get to the auditions? Abigail is good at taking the property of people she is loosely connected to so I wouldn't be surprised.

May 26, 2016

Cage spoke with EW about the possibility of a third film while he was doing press for his thriller The Trust, and he indicated that it’s research and fact checking holding up the development of the film as he told them, “I do know that those scripts are very difficult to write, because there has to be some credibility in terms of the facts and fact-checking, because it was relying on historical events. And then you have to make it entertaining. I know that it’s been a challenge to get the script where it needs to be. That’s as much as I’ve heard. But they’re still working on it.”

http://www.themovienetwork.com/article/national-treasure-3-still-way

Thanks
That's just my two cents.