It's not at all uncommon for long-running live service games to get dedicated sequels, simply because the original technology they were built upon ultimately requires a significant improvement. We've seen this happen with Rainbow Six, Overwatch, Smite, Counter-Strike, and soon perhaps even League of Legends.
A now-deleted social media post from leaker "Summoner Park" has claimed that Riot Games is well into development on League of Legends 2, and that it could make its arrival as soon as next year. X user Igenico has captured the post before it was taken down, where it is explicitly mentioned that the game will be built on a new engine, will remove legacy code, that it should revamp core game content, protect and retain the signature gameplay format, see major Champion optimisation and balancing changes, and more.
The statement explains: "Not only will it remove legacy code. But LoL 2's overhaul wouldn't stop in-engine. Park further claims that "champion abilities are also expected to undergo large-scale optimisation and balancing changes, whilst retaining champion identities."
<social>https://x.com/igenico/status/1987806832774267021</social>
The big question is how Riot will approach the immense workload that will go into bringing all of the 170+ characters into a follow-up title, and what kind of strain that will place on the production of fresh content. Also, how will this affect the cosmetics that fans have spent over 15 years collecting, and what about ranked ladders and performance stats? There's a lot of moving parts that various other games didn't manage to crack, hence why these live-service sequels are often so volatile, but regardless of the situation, League of Legends is getting on now and a meaningful upgrade would go a long way, especially for future-proofing the MOBA too.