No, they originally planned to make post ending gameplay as part of the vanilla game release, but cut it fairly early into development because it would have required basically another game's worth of content to make as they lacked the more dynamic systems Skyrim did for its civil war.
There was never any plans to make a post ending DLC.
I don't..... obviously. I felt it showed a rather realistic "end" to the main part of the war, which is all I ever wanted out of NV. Hell, if NV ended like Skyrim's civil war did, I would have had 10 times less problems with it.
Ultimately, NV's problems came from needlessly shoehorning everyone, their grandmother, and their kitchen sink, into a war plot that had no reason to have them in there, and then compounded the issue with an equally illogical and unrealistic attempt to force everything's result into immediate, when it wouldn't have. The only reason NV didn't have post ending gameplay was because Obsidian designed it just so poorly, in an attempt to feed into player's egos, that it lacked any sort of credibility or believable timescale to allow things to play out.
I actually felt fairly insulted by the way NV was designed. It all felt like it was designed just to hang over my shoulder, and tell me how [censored] cool I was, and how every time I blink the world had to explode. It is the worst kind of "consequences" a game can do. Greatly over exaggerating everything's result just to make player feel more important then they are, and to make player's actions seem more grave then they realistically would be.
To me, personally, consequences don't mean anything if they are like NV's, where one man's actions change the fate of every cat in the wasteland. Its so obviously fake, and designed just to stroke your [censored], that its impossible to take anything seriously, or with any amount of emotional satisfaction. Both Skyrim and Fallout 3, whose plots were literal Jesus allegories, and had the player fighting symbolic representations of Satan himself, had less ego stroking then NV did. Which is why I tolerate thier plots and endings better.
And before someone, not you specifically Demon, starts with the whole "THAT JUST MEANS YOU DON'T CARE ABOUT UR ACTIONS CONSEQUENCES!" argument, let me stop you right there, I do, I just ALSO care that my consequences aren't so overblown, and obviously designed to stroke the player's [censored]. and before you ask "but how can you be sure Bethesda can pull it off?"... they dd it in Skyrim, which i found miles more tolerable then NV.
Because its an entirely pointless waste of time and money to code something like that, when any decent made narrative wouldn't require it. Its a solution of satisfaction that has no reason to exist in the first place, so long as the design is even half-way decent to begin with.