Tatame is reporting that they have been told that the WEC will be merging with the UFC early in 2010:

Biggest MMA event of the planet, UFC has plans even bigger to 2010. Sources close to WEC informed TATAME.com that the UFC will add new weights categories on the next year, bringing athletes with contract with WEC, that was bought by Zuffa – same organization that commands the UFC – in 2006.

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On the next Wednesday, WEC 44 will define the featherweight champion on the fight between Mike Brown and José Aldo, what could, joining the events, define who would become the first UFC featherweight champion. Besides that, WEC has two more shows scheduled until January 2010.

We've been hearing rumors of the pending merger for months now.  Clearly at this point it is still a rumor but it is entirely possible that all the trouble with injuries has forced the UFC's hand.  Knowing that you'll have entire weight classes full of potential fights is likely very appealing when the promotion seems to lose another bout every other day.

We'll continue to monitor the situation and will try to get confirmation of the story.

Update:  Heavy.com spoke to the WEC's PR Director who said that there is no truth to the rumors of a merger.  I would say it could remain a possibility for the UFC to bring in fighters from the WEC to start two new divisions in the promotion while keeping the WEC around but at this point that is mere speculation on my part.