It seems that the rumors of an acquisition of Alienware by Dell are, just that, rumors. For most people, this comes as good news - it was quite a shock to hear of the enthusiast-oriented company being taken over by a mass-desktop oriented company. The CEO of Voodoo PC had this to say about the rumors:

"I'd suggest you take that speculation with a grain of salt given the origin stated in the blog (Alienware's competitor)--you can never be sure what the motivation is," McKeon told ZDNet Australia via e-mail. He also questioned the reasons behind such an acquisition, stating that Dell has the potential to be seen as a "cool" company and is more than capable of building viable gaming machines without Alienware's help.
Which makes perfectly logical sense. Dell already has "enthusiast" level machines for sale anyways.