the devs are keeping a close eye on the steam stats, to see quote "what the correct ending is". So I guess that the ending that most people play will end up being the base for future stuff. At the moment, it's Yes-Man/Wild Card. Which doesn't surprise me, as that's what I played too

I doubt they'll choose solely based on Steam stats, and it would be a mistake if they do. That's not because I favor the NCR or House endings as canon, but rather because more people will likely choose the Wild Card ending because it's the only one where the courier doesn't act as a patsy (if a powerful, well-rewarded one) all the way to the end. It's not because the Wild Card plot line creates the most compelling story of the four.
NCR winning probably has an 80% chance to become canon. Bad guys can always be created, and a Legion victory would wipe out New Vegas, so it won't be them. I don't know what happens to the courier if House wins, but I assume he would take his indie Vegas and make it even more indie, which just continues the standoff between him and NCR. However, the way he talks about a rapid evolution in technology with everything Vegas-related under his control could be compelling, so this probably has a 10% chance. Yes Man runs his Securitrons around stopping the chaos, which normally isn't interesting, but he does talk about becoming more assertive; give this one a 10% chance as well (though if they ever release post-Dam DLC, they might handle this possibility there). NCR winning, on the other hand, continues the progress of the Wasteland's lone stable government, gives several other factions a major power to work with or against, and the issues brewing in their government now will probably lead to some sort of breakdown that could fracture the NCR either before or during the next FO game, leading to the creation of brand new factions.
Some of those things could happen with a House/Wild Card finish. But with the Dam lost, the NCR would have to fall back, which means it would most likely either work to consolidate its power in California, rupture, or move north. If the next FO game takes place in some other location, like Chicago, then any of these things can happen and it won't matter. But if the setting remains out west, the first two possibilities will be a creative backslide, while a move north could work, although it would probably best be handled by treating the NCR as a peripheral player to the story. For these reasons, it's hardly a given that NCR will win. But given the future possibilities inherent in an NCR victory, they probably will.