XC2 shipped over 2 million as of 6/2020, over a year ago.

XC1HD shipped over 1.5 million 3/31/21, a few months ago.

XC1Wii shipped over 920,000.

XCX shipped over 840,000.

XC13ds shipped over 560,000.

If XC1HD beats out XC2 lifttime, it will only be because XC2 really pushed this series forward in terms of public awareness. Prior to HD, XC2 had more than double the sales of the next best selling Xenoblade game, and that's based on numbers that are over a year old (it's probably a decent amount over 2 million by now, plus all the money they made from the 160,000+ people that bought Torna dlc). XC2 is what lit the fire under the series' feet and so I think they will probably stick to that formula going forward, regardless of how people feel about boob sizes.

OMG really can't wait to see it if it's real

Hopefully ACE+ return to do the soundtrack, their work on 1 & 2 was superb.

Also Xenoblade 2 while a good game was somewhat rushed to release in the Switch's first calendar year and it showed, here's hoping having more time in the oven will give 3 a bit more polish.

Best news I had all day.

Xenoblade chronicles 1 is my favourite game on the switch, and the second one is also a masterpiece.

Eh, 2's soundtrack was certainly good, but it paled in comparison to 1 and to be honest from what I've heard (which is quite a bit, though I haven't personally played it) X's soundtrack is a lot better than 2's as well. 

I honestly feel like just going for the same style over and over and over again is just going to draw comparisons to the original, which has such a timeless soundtrack and shouldn't be the goal. If ACE+ changes styles for 3 that would be sick, or if they are somehow able to top 1's OST with a similar style that would be neat, but I think the latter is just super hard and the former might not happen if they just get the same group again. 

I'd agree if we were only talking about battle themes, and also the main and ending tracks, but I've always felt other songs from 2 are amazing standouts, especially the area ones. Uraya's day theme, Alba Cavanich's night, Spirit Crucible Elpys, the LEFTHERIA themes, godammit. The Leftheria songs are among my favorite video game pieces, period. Walking With You and its instrumental version, Desolation, are beautiful, too. So are various of the tracks that play just before the ending (no, not talking about One Last You). Those are memorable to me than the vast majority of the original's soundtrack, even though I do concede that it has the most bangers. Even Riki's theme is cool. 

I think both have area themes that aren't as good as their battle themes, from what I remember. I think they get a bit formulaic. It's been longer since I've played 2 for example, but when I played 1 I remember finding the dynamic of the day and night themes a bit generic. The night them was always just a slower version of the day theme, with a relaxed atmosphere and usually some kind of piano. Again, the themes were good themselves, but they suffered from being part of a formula. I think the areas themes can be a good example of how something simply being "beautiful" or "epic" isn't always as important as being interesting and intriguing. 

That being said, I feel like Gaur Plains, Sword Valley, and especially Satorl Marsh daytime (super underrated) are better than any of the area themes in 2. Again, from what I can remember. 

Oof, hard disagree on that.  While I can understand preferring 1 to 2 in the soundtrack department, to say it pales...nah.  I would say they both beat each other out at different points.  I think the battle themes are better in 1, the field themes are about even, and the town themes are much better in 2.  The vocal tracks are tough to compare, sinc they are very different.  But I think they are fairly even.  Though I think A Moment of Eternity is the best of the vocal ending songs.

And as a big defender of X and its style and music, I would still say 1 and 2 are better.  X's is more unique though.  It's also hurt in game by bad track usage which is less the case in 1 and 2.

But I can understand wanting a new style.  I personally really like the stylistic adjustments they made with the new tracks in Torna which still soubd similar but have a different vibe and a jazzy feel.  Would like to see something like that taken to the next level with a third game.

I thought the OST for 2 was packed with bangers and a lot better than X's very inconsistent score, which had some cool tracks but also some painfully bad ones. Tracks like these rank along 1's very best for me.

I like Satorl Marsh daytime a lot more than its counterpart, it's my favorite track from 1, I'll say. 

If the themes are good but they suffer from being in a formula, isn't the original guilty of the same thing, then? Gaur Plains is just like you say, and the dynamic with Satorl Marsh was just inverted, though both songs seem different, that I admit, which is exactly what happens with Sword Valley as well. However, many of the overworld themes nonetheless still function a lot like the other two games. That makes me think you still judge the tracks a lot based on their individual merits, and not exclusively or primarily on how unique they make the soundtrack as a whole. Your last sentence in your first paragraph makes me think I could be misunderstanding somewhere, but I'm not sure.