Wario's Shipyard was a bit of a reference of sorts to the first two Wario Land games,
The pirate theming, the music track having some minor Wario Land influence,
And a cameo of Bull Wario
It's not obivous like DKC and DK Island, but the track does have a very Wario Land vibe.
And it's probably the closest to a Wario Land based track we have in the Mario Kart series. (Even if it's not directly based on anything from Wario Land.)
If we're lucky, some sort of background/musical reference like in Wario Shipyard. If we're even luckier than that, we'll get a Wario Land themed track, though given Diamond City only appeared in the arcade games, it seems spinoffs aren't high on Nintendo's priority list there. And unfortunately, the chances of a Wario Land character in Mario Kart is virtually nill, regardless of how much Captain Syrup would be neat to see in a Mario sports title.
Just to answer the topic, most likely very little similar to previous games.
We'll probably get something like Wario Shipyard again where it's clearly inspired or influenced by Wario Land or maybe the Wario Car could come back as a Kart.
But I sadly don't expect to race around Wario's Castle as Captain Syrup in Wario's Car anytime soon unfortunately.
Maybe we will get something great in the future, but I'm not expecting it for awhile.