Which to me certainly sounds as though they are confident in their tennis title. "With full blown tennis battles on hazardous courts, varied missions that challenge your skills, and monstrous bosses standing in your way". Mario titles, perhaps especially Mario sports titles, aren't exactly renowned for their narrative prowess.
In addition to Luigi getting his hands on what appears to be the Infinity Gauntlet of tennis rackets, the cutscenes also show Wario and Waluigi in some spooky new forms.
Today Nintendo revealed that the pre-launch tournament of Mario Tennis Aces will take place from June 1 to 3 at 23:59 JST in Japan, date that should be taken as a reference for the celebration of the competition in Europe and the United States, since it is thought that in these markets will be made in later days. In the trailer, we see some sort of dark energy taking over Luigi, and it seems that it has already taken over Wario and Waluigi. Pacific, 9:00 p.m. Eastern. Nintendo also states that "all participants" will be able to unlock a free additional costume-Mario's traditional dungarees-for use in the full game, though it's not now known whether you must achieve some feat to unlock this or if it's awarded to you just by taking part. It will be going live on the 1st of June and will run until the 3rd of June.
All participants will be rewarded with Mario's classic outfit in the full game, and it is unclear at this point whether there will be another opportunity to procure the familiar blue overalls, so if you're a traditionalist, make sure to jump in!