I'd certainly like to see your factual evidence for which you reached this infallible conclusion. I don't see any 100% concrete evidence that says "If it was blocked off in the beta, it will be available for purchase later as DLC". So you've technically wasted all your time researching only half the story.

Please cite a credible source that states the blocked off areas in Old Russia will have anything to do with the DLCs. It's far more likely that those areas were simply blocked off in the beta/alpha because they are meant for much higher level characters, and Bungie didn't want anyone going there. I can't find any confirmed information about House of Wolves that even mentions where it's going to take place at all. The Dark Below is said to let you explore "the true depths of the Hellmouth", which is already a location, yes... but "true depths" implies it's going to be much larger than what is in the launch release. Not to mention, any blocked doors in the Hellmouth we could explore on the Moon were likely part of other missions/the Strike involved in that location. The same way you can run all the way up to the Devil Walker in the Devil's Lair areas of the Strike in Old Russia, but can't actually enter Sepkis Prime's boss room unless you're actively playing the strike.