Total assumption here but id imagine when running the matches on your developed cards, you will be able to have other players participate in your matches, if you choose to play your matches instead of SIM.
If I remember right that seemed to be an option on the gba though that would have required a link cable.
I'd like some more details really. A video dropping this week or next would be great. We're less than 2 weeks away now though.
A video. Anything beyond maybe a five second tweet like two days before it comes out, which probably announces that the DLC is getting delayed. Hoooo boy, that's rich.
Not to turn into the eternal pessimist, but like, nah, dawg... ain't gonna happen. They have really dropped the ball on any kind of marketing and messaging whatsoever and considering this bug that's been introduced with the most recent patch they may very well be in panic mode to try and get that fixed as well before the DLC release. Point is I wouldn't expect anything beyond either A) the DLC just drops with no kind of fanfare beyond a pretty boilerplate "Hey it's out!" tweet with a short .gif or 30 second-long video on the day of release, or B) there's an announcement a week to like two days beforehand that it's delayed.
I'd really, really love to be proven wrong, but, well... I haven't been with any other DLC or patches.