Set aside genre lables which have been proven time and again to not matter to people.  Looking at the game itself, I think the franchise could sell two to three times what it has in the past, with some games selling more than others.  The X series probably has more mainstream appeal than the mainline though, as both the first one and this one have some unusual aesthetic decisions that may put some off.  But even then, not a guarantee it would make a difference.  The real time battle system used in Xenoblade is similar to numerous systems enjoyed by millions in big selling games.  Shoot, the MMO genre is *built* on this.  And it isn't just WoW keeping it alive, Final Fantasy XIV is the fastest growing MMO and uses this same style of system.  

The real question is how heavily and how consistently Nintendo is willing to push the franchise.  And of course how good that push is.  We'll just have to wait and see.  

Yeah, I felt the same way, and discussed it with some ppl in a different topic.
I used to be hype for Xeno trailers, but for this game it's had the adverse effect on me. Though I'm still keeping my eye on it.

I hope it does well though, as a longtime fan of the Xeno series.

Btw, are you Majin Tenshinhan on Eventhubs? https://www.eventhubs.com/profile/MajinTenshinhan/

I am looking at the game itself; it simply doesn't seem mainstream enough to do 2.5 million. There's a big difference between what's huge on PC and what's huge in the console space.

Could the series itself hit these numbers? Yes, I think it could. But it would take a game more stylistically and mechanically in line with what is popular in today's console market to do so.

FFXIV has considerable presence on consoles.  And things can shift as well.  I mean, Person 5 is doing way better than a console Persona game has ever done.  

I honestly think the game could sell 2 to 2.5 million, the mainline games.  X, if it is consistently similar to the first X, could sell 2.5 to 3.5 due to it's more mainsteam visual style and world strucutre.  It's a matter of how they market it, highlighting the things that make it mainstream.  It's fantasy, that's mainstream.  It's big and epic, that's a huge thing now.  It's open world, that's big.  It has a lengthy storyline, which contrary to what some publishers think is still quite desired.  Maybe the character design hampers things for Xenoblade 2, but then again Bethesda Game Studios has struggled with character models for ages and their games have exploded in popularity so that may not matter nearly as much as some think.  And 2.5 is not, imo, all that big.  It's a nice number but it's not like I'm saying it will do CoD numbers.  I don't know if 2 will pull that, I kinda doubt it because you normally have to build popularity over multiple releases so it would be unusual to go from 980k to 2.5 million.  But then let's not forget Fire Emblem Awakening, which took the franchise from life support to 2+ million.  And that, imo, is a far more niche gameplay style.  And it went full anime as well.

FF14 has a massive brand name to push it though.

And Bethesda's titles appeal more directly to current Western tastes; namely, a bit more grit and "edge" than XB2 seems to offer, plus being more mechanically straightforward. If XB2 can hit 1.5 million that would be a victory in my book for a series that as yet has never broken the million mark.

Heh, I didn't know you were Swedish. Are you Ghandi? ;)
I've seen your name around here and there on Eventhubs and Twitter since I started following the FGC around 2010. Small world I guess.

Those tastes were not established or noted really when Oblivion exploded onto the scene, doubling the sales of Morrowind.  And Oblivion wasn't all that edgy really at all.  

And as I said, a 1.5 million is what I expect.  But I think that could be a stepping stone to 2 million and beyond as the series goes on, with mainline Xenoblade being a lower selling franchise probably than Xenoblade X.

As I recall, (I was still in high school at the time) Oblivion very much rode the wave of the "Wow, HD/next gen/biggest most immersive world ever/you can go anywhere do anything" hype. But that was a long time ago; 2007 and onwards established a trend of AAA Western games being gritty, bombastic, etc and Bethesda continues to successfully tap into this.

If they made a XCX sequel with a better story, less padding, less convoluted/more streamlined mechanics, and very strong marketing, than that I can absolutely see that hitting 2.5 million. For here and now with XB2 though, I think those kind of numbers out of reach for the moment.

Bolded: don't even think that would need doing at all.
Italics:  This on the other hand, is THE key.  More than literally every other thing you listed.  Honestly, XCX should have cruised by 1mil with ease even on the Wii U.  That it failed to do so is a catastrophic failure on Nintendo's part.  The game had so many aspects that appealed to the mainstream it should have at least outsold the first.