with Matt being the purple tamer and Tai being the black tamer, I have a theory that those tamer cards were supposed to be for other characters debuting in the Adventure: 2020 anime but due to the hiatus, the anime and TCG were desynced resulting in Matt and Tai filling in for those characters.
100% a headcanon but who knows?
It's too early to say there won't be other characters in the series, I mean I really do want to see more at some point, but I don't think this is all that likely a scenario. Tai fits black simply because there are black cards related to his partner, i.e. Machinedramon, BlackWarGreymon, ToyAgumon, etc., and gameplay-wise black is the opposite of red (as can be seen in this Tai having the opposite skill of the Gaia Red Tai). Matt might've been chosen simply because he wears a purple sweater and is the deuteragonist of the show who gets as much focus as Tai lol. That said, we might see Garurumon going down a darker evolution path for an arc or something, but that's also just speculation.
I think, if there are going to be new characters, they'll get Tamer cards much later on and have nothing to do with these cards. I think the second set is too early to start introducing new characters who haven't been featured much yet if at all. Once we get the Kari card (which
could be this set, to be fair), that's when I would start to expect they'll start introducing any new characters if they exist.
Putting "God" on Mitamamon's Type instead of "Holy"... Don't you think "God" is a bit too strong for that digimon partner? Hoping we'd have another Holy Beast type but it's pretty huge surprise.
To be fair, I'm pretty sure Huanglongmon has only ever jobbed during its appearances, so this is an example of a God Beast that's actually going to get to do something lol.
Besides that, is it all that different from someone getting the highest level Angel, God Man, or Holy Knight Digimon as a partner?