343 stated in a Game Informer interview awhile back (late 2011 or early 2012, if I recall? I believe it was a few months following Halo: CE Anniversary's release...) that while they currently had no plans to make a Halo 2 "Anniversary", they would consider it in the future.
While it's not much of a confirmation, at least it shows it has crossed their mind, and that they will most likely do something regarding it within the next few years, I'd say.
Personally, I bet we're going to see SOMETHING from 343 at E3. Whether it's just a teaser for Halo 5, or maybe a Halo 2 Anniversary trailer, I think it will be one or the other.
I think it'd be realistic for us to get Halo 5 no earlier than Fall 2014. So, honestly, I could see them releasing a Halo 2 Anniversary before then (to tide us over?). Or take the same scenario and add a year to both: where we'd get a Halo 2 Anniversary in 2014 (which would make more sense, since it would be the 10 year anniversary of the game), and then we'd get Halo 5 in 2015.
Perhaps it would even be a launch title for the Next Xbox? I'd still take it if it was just on the Xbox 360 though. Guess we'll have to wait and see... I'm sure we'll find out something throughout E3.
IRON MAIDEN IS MY RELIGION! Gamertag: Demigod Elessar