Looks like someone planned further ahead than Infinity Ward, because a game community site has allegedly registered the website domain “ModernWarfare4.com”. And on top of that, the site includes an infuriatingly stupid demand for Infinity Ward to obtain the rights to use said web domain.
The site was registered on March 26th 2009 on a UK server, and this is the message that is posted on it.
We’ll wait for the official response for Infinity Ward on this, as well as Ziip’s. But rest assured, if the site truly is owned and maintained by Ziip Gaming Community, the courts are instantly going to decide in the game developer’s favor.
[Source]