Chaos Space Marines aren't on the immediate release horizon. This particular Son of Horus would love a new Chaos Space Marine Codex that features the Legions prominently and above the random other traitors that nobody cares about, but we'll see what happens.
All I know right now, as a store owner and GW shareholder, is that they're currently in development, which means we've got at least a full quarter before we see them if not longer.
IN THE US? ASK ME HOW TO GET 10% OFF GAMES WORKSHOP PRODUCTS!