It looks like Neo is back. Keanu Reeves along with Carrie-Anne Moss both announced that they will be back for a 4th Matrix movie.

Also returning is writer/director Lana Wachowski who, along with her sister did the first 3 movies.

As of today, there were no other announcements of other cast members.

The first "Matrix"  movie was released back in 1999 and was followed by "The Matrix Reloaded" and "The Matrix Revolutions", both released in 2003.