Well, they'll still provide more lore to the Fallout universe and have some slight connections to the main game. (Elijah, Veronica's former girlfriend Christine, Ulysses, Courier Six)
So in the long run it might provide something to the main game.
But as it currently stands I see it as it's own little game and not part of the main game.
Best way I can explain it is this way:
You know how when in some games you can continue past the main quest but nothing changes?
Well, when that happens to me I'm like ".... Now what?"
Same thing happened here.
In Dead Money I was not The Courier.
I was The Puppet, and I completed The Puppets own little story and it wrapped itself up nicely.
But after that I'm thrown back into the main game as The Courier and I wonder "So what was the point of me going there? What has changed?"
Nothing.
Nothing at all.
I can give Veronica a holotape but that's pretty much it.
Oh and I get some fancy new toys to play around with.
But did this epic SAW inspired adventure actually serve a purpose to my character?
Nope.
This DLC would have served a better purpose if it was like that Darkspawn DLC for Dragon Age, where we get to play as a new character.
That would have made more sense to me, to play as a completely new character, The Puppet.
Where the story starts from scratch and by the end it's the end.
Only connection I can find is the "Things of the future" thingie where it's vaguely explained we have a connection to Ulysses.
And those are only subtle hints which could easily have been dropped.
All they're there for is to create suspense (which they did a good job with) but they don't serve much purpose to the actual storyline in Dead Money.
So Dead Money, was fun as hell, great story, great atmosphere, great writing, great characters but I didn't feel like I was The Courier when I entered it or left it.
Again, when leaving it I had a question mark on my forehead.
Now what?
I did this epic adventure and now I'm back to hunting gecko's and doing courier jobs for NCR/Killing NCR?
Would have been better if we were a new character and the story ended right there IMO. (With new items added to main game merchants/generic NPC's of course)
/Opinion.
I've said before on here that I've liked all of the DLC's so far in Fallout 3 and New Vegas but, you are spot on here.
I loved dead money and it really wasn't what I was expecting from a Fallout game at all, it was nice to be taken from my comfort zone and change the game around a bit but, Why must me lose our inventory? Your' right, we might aswell be a new character and it has no realtion to the main game bar a few posters here and there and a couple of dialogue's. Nothing changes in the world at all and the events feel insignificant.
I think it's a missed oppertunity and DLC that ties into the main quest and sotry will always be better to play and more interesting. I want to be my character, I want to feel like my character and all of the things I've bought, found, killed for and spent hours building up I want to take with me and use!
When the main quest/story is so good, why not add to it or atleast relate the Siera madre to it in some way and have the ability to revisit afterwards maybe under NCR or BoS control?
Like I said before I loved Dead Money but you are spot on, we need continuation, story relevance and aftermaths!