This is crazy (and not so crazy at the same time).
It looks like Link could be coming to Mario Tennis Aces. Not only will standard Link in his green tunic be joining the roster, but it also looks like Dark Link and Breath of the Wild Link will be coming, if a datamine of the game is to be believed.
This is quite believable as Link came to Mario Kart 8, which was incredibly surprising at the time.
Nintendo has been very good with providing content to Mario Tennis Aces, with a new character being added each month for those playing online. Unfortunately, numbers online has dropped significantly online (I should know, I’m trying to get a match online every night).
It’s unclear when Link would join the game, but we currently know about the characters launching until the end of February.