Last week we saw Dark Vengeance getting pulled off the shelves, and yesterday had word of a new starter set for 7th edition. This sets up a perfect opportunity, and sets up with rumors, that a Chaos Space Marines release is likely coming soon.
A while back we had a lot of detailed information about coming releases, talking about a veterans of the long war supplement, new chaos marines, and chosen being released. With access to Dark Vengeance models now gone, it only seems likely that the opportunity to sell new kits with these models is due.
Here are some links to the previous rumors regarding Chaos Space Marine releases.