Vivendi Games and Activision have merged into a single company called Activision Blizzard. While the name has Blizzard in it, make no mistake, Vivendi Games is the parent company of Blizzard, and while the name has 'Blizzard' in it, it is Vivendi Games that has merged.
Blizzard posted on their forums to the effect of saying that there will be no changes to their games, their staff, their offices, nor their development teams. Blizzard Entertainment will continue to function as a division -- the only difference being that their parent is no longer named Vivendi Games, but now Activision Blizzard.
So to those wondering: no, there will be no changes to Battle.net as a result of this merger. Battle.net will operate as usual.
Yes, I already have sent a direct request for comment to Blizzard in regards to how Battle.net will be affected, but most likely their response will be similar to their post on their forums. If there is any different information than that posted on Blizzard's forums, I'll make sure to let you know.
If you'd like more information on this, feel free to email Blizzard at email@example.com.
Blizzard's forum post
Activision Blizzard Press Release