As much as I would love to see this happen, unfortunately I have to disagree with this. If they made a remake of Halo 2 for the 12th anniversary then there could be 2 things that will happen. First, Halo 2 will die because of the amount of players staying with Halo 4. Second, Halo 4 will die because of the amount of players moving to Halo 2.
Also, there was no matchmaking for Halo Anniversary, so there probably won't be a matchmaking for Halo 2. People would only expect to play online for Halo 2.