Ahem!
Obsidian is making or charged 7 Add-on(DLC) for New Vegas, not Bethsda. What are you, hide under the rock?
This source is almost 100% likely to be false. There is no reason to take it as fact, and using the "hiding under a rock" expression is a bit uncalled for.
Expect 4 DLCs. Game files, trademarks that Zenimax just placed, and snow globe space all point to 4. It's possibly we may have more, but I would count on 4 so as not to be disappointed.