Many have wanted this to happen for years (especially after the spin-off series that happened in 2007).
Source
Official anime site
Video announcement of the anime adaptation:
If it wasn't made obvious already by the trailer, the adaptation will follow the original game, so with that in mind the original voice cast will stay the same. This just keeps getting better and better.
Count on the official site is for the release of Gakken's Megami Magazine, which will feature more information about the project. Can't wait.
Also keep checking the site everyday for the
written messages from the voice cast.