Had a scare when first hearing this. But somewhere else on the site it does specify this as something like “some physical games”, and as quoted in OP they’re contrasting here with “regular game cards”. So it looks like real game cards will still be a thing.
So far I’ve seen screenshots of SFVI and Bravely Default boxarts marked as game-key cards.
I’ve seen box shots for Mario Kart and Donkey Kong that appear to be normal game cards.
I’m not big on the idea of open world racing. To me, driving between race tracks looks like a chore.
I’ve seen other racers do it, but I’ve never really delved into a game like that. Maybe once I do I’ll really like it.
I do think grinding rails and wall jumping around looks pretty fun in MK. But it could end up gimmicky and unexiciting once you’re used to.
Basically all a big ‘wait and see’ from my perspective.