One of the most treasured franchises (see what I did there?) in Nicholas Cage's film catalog is Disney's National Treasure. After National Treasure: Book of Secrets, we have heard countless rumors that a third film is happening at some point, but not much else that was concrete.
In Walt Disney's 2016 shareholder meeting, a question came up asking if we would see another entry in the franchise, and Bob Iger had this to say about the project.
We have done two, and yes they were really fine movies. I know Jerry Bruckheimer who produced them has had conversations with our studio a number of times about it, and there have been some developments along the way, but as of right now we have not green-lit as we say, a National Treasure 3. But I do know there is time and some resources spent on development. That's all I can tell ya.
It doesn't seem like a priority at the moment, but at least it is on their radar. Hopefully soon it will make its way out of development limbo, but for now you'll just have rewatch the first two.