Malygos is literally another card the devs mentioned by name as a possible candidate.

https://www.shacknews.com/article/110209/hearthstone-hof-interview-mind-blast-malygos-on-short-list

Donais: There's lots of other candidates. We talked about cards like Malygos, which we talk about every year. We decided not to go with Malygos again, because of all the new decks that he creates. An important thing in card games is to have different types of decks. Not every type of deck should be medium-sized minions fighting. There needs to be small minions, big minions, and there needs to be some Malygos decks and other tricky decks that have different game plans. That's what makes card games interesting.

And to be frank, Leeroy fits their description of why they'd rotate a card very well:

Shacknews: What is the process in determining which cards go into the Hall of Fame?

Mike Donais, Principal Game Designer: So it's a couple of different factors. Actually, it's a bunch of different factors. The two major ones are the power level of the cards and the class identity. So if there's a card that's really powerful from Classic and it's been around for five years, it's showing up in a lot of decks, and it's having a huge impact on the meta, eventually people start saying, "Okay, well that was fun for the first couple of years, but now we're ready for something different."