With Warner backing Blu-ray, there are numerous rumors stating that Paramount will follow suite and drop HD DVD in favor of the rival format. According to a report by the Financial Times, there is a clause in Paramount's contract with the HD DVD camp that would allow the studio to switch sides in the event of Warner Bros backing Blu-ray.
Paramount is poised to drop its support of HD DVD after Warner Brothers’ recent backing of Sony’s Blu-ray technology, in a move that will sound the death knell of HD DVD and bring the home entertainment format war to a definitive end.

Paramount and DreamWorks Animation, which makes the Shrek films, came out in support of HD DVD last summer, joining General Electric’s Universal Studios as the main backers of the Toshiba format.

However, Paramount, which is owned by Viacom, is understood to have a clause in its contract with the HD DVD camp that would allow it to switch sides in the event of Warner Bros backing Blu-ray, according to people familiar with the situation.
With Blu-ray having a strong showing at CES, it would not surprise me if Paramount switched sides and dropped HD DVD. If you'd like to read more, the entire article can be found here.