Well, if it turns out to be good, I think it'll be between 1-2 mil LT. It could end up being the best selling if it's a combination of the game being good and the continued success of the Switch.

"~~~~ Mario Tennis Aces shot far past my expectations! Never again will I doubt the racquet of a Mario Sports Franchise! :0 ~~~~" 

0.5M if its an empty shell of a game like Ultra was on WiiU.

In needs to have the same features as a real tennis game, i.e. save progress of matches, sets, tournaments, records, title wins etc.. maybe a career mode equivalent but that I can live without

1.43 milli

All games are selling great on Switch so far, so I will say 2m+.

Mario and Rabbids is looking to sell more than 2 million (and the DLC isn't even out yet) so I can't see why anything else Mario branded can't. After all, it was a new IP and the genre was more niche (although Tennis, in particular, could be considered a niche sports subcategory for games, not sure)...

I think you guys are forgetting the Japanese market. The first Mario Tennis sold 1 million in Japan, so it was appealing to them more than anyone else. So what we're looking at here is, can this game sell 1 million in Japan? It's a tough call, as the 64 wasn't that popular in Japan, yet this game did somewhat better in the region than any other game in the franchise despite the latter entries on the Wii and 3DS having a far bigger install base in Japan.

So we could say, "yeah, it definitely is a franchise declining in sales" as I hear that Power Tennis wasn't bad, not one bit. I often do hear that Mario Tennis Open was mediocre, though.

Whatever the case is, I believe that this game should at least sell 500k or more in Japan, and the other regions should hit that amount too. I'll safely go with 1.5M...but I know it can top 2M easily. Depends on how good the game is at launch honestly, but it should be better than Ultra Smash.

I think best selling Mario tennis game. 2.5 WW

I was expecting 3.5M before reading the realistic breakdowns of other posters. I think the game will be very well-received if it is a lot like Power Tour.

I'd say 1.5 - 2M. Besides Smash this should be the main focus at this year's E3 – and the new online mode with events comparable like the Splatfest should interest a lot of people.

I'll play safe and say 1 million. Surprisingly there hasn't been a lot of party games from Nintendo on Switch outside 1,2 Switch, that might help push Mario Tennis Aces higher.