I'll go with around 3.5 million. For the bonus I dislike it since I prefer to play games when they're complete but if Nintendo keeps using that model it probably works out well overall sales wise so nothing really can be done for those who dislike it.

I think it hits 5 million. Mario Tennis on Switch hit 3 million, and I think Soccer is just more popular.

As for the bonus question, if Nintendo thinks that model is better at increasing engagement and getting more sales, then that's their right. If you don't think a game has enough content in it at launch, then you're free not to buy it.

As a potential buyer, I'm on the fence about it. For instance, Switch Sports really doesn't have enough content for me yet. We know Golf is on the way. I would assume more sports would be added in the future, but in the past, I bought games believing more content would be added, and that hasn't been the case, or the content hasn't been worthwhile enough. For instance Mario Golf and Marip Party Superstars. So, this time, I'm going to sit on the fence, whereas if there were 2-3 more good sports I would buy it.

As for whether the content is in the game's code or not, I don't find that detail especially relevant.

Bonus: I dislike withheld content and it sucks that Nintendo is going down the same route as everyone else. I miss finished games and actual DLC being special or unique. As long as games have challenges and some sort of reward locked behind that then I would keep playing a game I like. I'm fine with cosmetic unlocks coming through live service model, but Switch Sports missing sports and Pokemon Diamond/Pearl releasing unfinished is what irritates me.

I was very early into digital purchasing almost everything with PC and Xbox Games on Demand (back in early-mid 360 era, especially because I sold Halo 2/3 accounts for microsoft points), but the last few years I have reverted and now almost buy exclusively physical releases with the occasional boycott of digital only games (well...only on Epic store). I want complete games on the cartridge, and if technology improves give us our cartridge tied saves back.

It seems like this game should eventually sell 1 million. I don't know if it will sell 2 million though. Probably not.

Over 5mil. It's gonna get more and more content over time and had really good launches in France and Spain. Japan and UK don't really paint the whole picture there.
I expect it to have very good legs and end up ahead of Mario Tennis Aces, which should be over 4mil by now.

Bonus: It's generally a bit annoying, but I tend to buy these games only months after release, so I personally don't mind. It does affect the games reception at launch though, which is a shame.

It seems limiting content at launch and releasing it over time is Nintendo's way to limit the experience for hacked Switches. It sure made me not want to buy it as I was actually excited about in the benninging. I don't like how Nintendo is locking parts of their games behind a digital wall!

anywho it will probably do around 5m

I expect it to sell a million, but not much more.

Does Battle League have a lot less content then the other Mario Strikers games? People talk about it like it does, but the other games looks equally barren based on videos that I looked up.

1 million? Are you sure?

The first Mario Strikers on the Gamecube sold 1.6mil and Mario Strikers Charged sold 2.6mil. Both were the best selling Mario sports game on their console. Mario Strikers Charged was the best selling Mario sports game as a whole before Mario Tennis Aces outsold it.

Mario Golf: Super Rush sold way over 1mil in it's first week and Golf has always been less popular than Strikers.

Mario Strikers Battle League is likely already over 1mil by now, even if it had a smaller launch than Mario Golf, which we can't be sure of.

It doesn't have FIFA in the name so it will sell poorly.

Over 5 million probably. Nintendo will sell a lot of Software this year.