The overall market will deteriorate the longer they wait. Interest will wane. People will move on. The game is aging. Period. End of story. It's simple economics.
I have my doubts as to this. Generally speaking, people will hear about the new DLC release from the interweb/friends and check it out, even if they've "moved on" from the game. We saw this in Fallout 3, we see this in ME2, and we'll probably see this in NV.
If you're the kind of person to enjoy New Vegas to begin with, you probably aren't really going to "move on" so far that you won't be willing to come back when new content is released.
You can see examples of this in Mass Effect 2. The DLC well has been pretty dry for months, with only the Arrival DLC announcement breaking things up (and, in fact, interest in ME2 has been undermined by the ME3 teaser trailer), and yet everyone I know is planning to get Arrival, just to see whether the possibly-faked screenshot about sacrificing Tali is accurate. Heck, I haven't put the ME2 disk in for months at this point, yet I know that I'm going to buy into Bioware's monopoly money scheme just like I did with Lair, simply because I want to see the story. Most others I've talked to feel the same way.
RPGs are a different market than flash-in-the-pan shooters like Resistance Call of Halo: Black Operations in the Killzone (Gears.) People who buy such games are used to only getting X (<20) hours of gameplay out of them, maybe a few more for multiplay. People who play RPGs, meanwhile, generally expect longer games. An RPG that only lasts twenty hours is considered pretty short in most circles. In other words, the attention span of RPG players is typically a bit longer than the attention span of shooter players. Or, perhaps it would be more accurate to say that someone who buys an RPG is looking for long term content - and hence is more willing to wait for additional content - than someone who buys a shooter.
This forum is like high school. You have the loud, vocal, "cool" crowd who generally has NO idea what they're talking about.
I find this pretty funny. You've never really impressed me with your arguments on any subject. You generally state your opinions as fact with nothing to back them up, then when someone provides arguments that are contrary to your prefounded opinion, you ignore those arguments and try to denigrate the other side rather than actually refuting the arguments. Alternatively, you continue to assert that your opinions are a valid refutation of logical argumentation.
In this particular instance, you're basically making an appeal to popularity when there's no real information on the market. Now you
could be right. Anecdotal evidence from my experience says you aren't, but either way, your argument is lacking in actual evidence, and hence, isn't a good argument. You're basically saying "oh hey guys, you're all wrong because clearly there are these huge masses of casual fans who've already moved on. You all are just a vocal minority."
Problem there being that there's no evidence on what this supposed majority wants. It's the same problem with all those "freeplay after the end" people. They always say the fans want this, but nobody knows what the majority of fans want because there have been no studies done on the subject.