I agree with your first point, I would love to have a large expansion to New Vegas than just a small dlc. However, there are only 4 dlc confirmed at this moment, but there are rumors that there might be up to 7 dlc released over time, according to the Vault: "According to one video game news blog[9], a source "close to Bethesda Softworks" spoke to journalists on condition of anonymity, saying that four DLC's other than Dead Money were in development as of December 2010, with two others being considered, which if approved would make for a total of seven add-ons for release over the next two years. Of the four DLC's planned for release after Dead Money, the source was said to have stated that the Courier has a "relationship" with Ulysses and that the nature of the relationship would surprise players. He also said that a future DLC would add an area to the game that players "likely thought they would never see", as well as "a personality [from] Fallout 3".
I believe that source to be an utter piece of crap that is perpetuating a rumor. For one, they say "A source reliable to Bethesda" which shatters their credibility from the start. Anybody can say this. Also, later in this statement (on the actual blog) it states that there are 8 DLCs, and it only says 7 on the wiki because whoever edited that into The Vault actually counted correctly. The blog also says that Ulysses is the Courier's lover, which either shows that this entire blog made up the source, or that they did get the source from somewhere and took the "nature of the
relationship will surprise players" comment as "Ulysses is the Courier's lover". All signs point to this being false.