Well, to make a resectable opinion, you have to answer a question first... What is the goal of Matrix Revolutions? (assuming it's the last in the seris)
1. The goal of the first and second: Free everbody from the Matrix.
How to solve: More movies

. I'm sorry, but there is no way on earth this problem could be solved fast. In fact, if there is a resolution in the next movie... they only will get the machines and agents out of thier way, then start the slow process. But, what may really happen is the Matrix being competly shut down... and the outside earth forming from only the people of Zion.
Which brings up the question, can humans survive without the machines? Is the earth a place where humans can realy survive? Is life better with the machies?
2. Save Zion from the Machines
How to solve: Some would like to belive Zion is a Matrix outside the Martix, and hopfully this is true or the humans are in trouble. But wait, didn't the Archetect offer Neo a way to save Zion by starting over? Why? Simple, the Matrix needs Zion. Some people in the Matrix can sense that they were in a program, and they could be potentially dangerous. By freeing them and giving them a impossible goal is means of control.
Neo is controlled, he has been being pushed around by CPU programs to achive an ultimate goal. But Neo made one decision that may not have been expected by the Matrix... he saved Trinity over saving humanty on the outside as a whole. That wouldn't have been the move I would have taken, but eh somehow he
had to be special compared to the 5 "other" ones for them to make a movie about him.
Now, the matrix needs Zion as an area to place and kill minds that sense the fakeness of the Matrix. But, Neo chose not to save Zion so, once again, it will be desroyed... but this time without a way to be Revived. (at least not a way the CPU will have control over).
My personal concluson here is that Neo and Morpheus are under some type of mind control program. The program goes by the name of The Oracle. The CPU must have always looked for ways to control "The One" by giving him a false purpose. Also, like I said a cople of times before, a way to cotrol Zion. The "Prophecy" that Neo and Morpheus live by was created by the CPU.
Now, back to how to save Zion, well, it brings up another question. How did Neo stop the Machine at the end? Well, because the Matrix needs Neo, I think Neo was spared (yes, saved) for the good of the Matrix. Why is he needed? I have two ideas:
1) The One is needed to develop Zion, without him, no more Zion...
2) and the second reason he is spared is also the third goal of Matrix Revolutions:
3. Defeat Agent Smith
Smith may be the single worst Virus the Matrix has ever had in history. Given time he could completly run the Matrix, if all of his copies keep making copies maybe one every minute, he would be the only person left in the Matrix, and we all know he hates the Matrix, so he could commit a mass suicide on himself, kill all human life, thus killing The Matrix's energy supply, and destroying everything.
Who can defeat him? The other programs can't, and the Matrix really can't crack down on him... this is a job for our superhero Neo. I'm guessing he has to destroy the "real" Smith, or the one who started the virus. He/It may be powerful as hell and I think we may have seen him in the Matrix Revolutions trailer.
If you want my honest opinion, I think if nothing is solved in Revoluions, at LEAST Smith will need to die.
I feel that Revolutions isn't the last Matrix Movie, I think Revolutions/Reloded are all one movie that will be part 2 of a trilogy. The goals haven't been cleared up enough in Reloaded. The next movie may need to be a good 4hrs to answer everything.
Matrix is the Next Cult classic, kinda like Star Wars... There are even more side stories in the Matrix. You think SW had a lot of video games, I think Matrix will be able to match it in the next 10 years alone. They could also make prequals, and sequals like Star Wars too.
-EDIT-
I gots a question, what is the "Zion Mainframe"? Why did the agents in the first movie need the the passcodes for it?