Riot Games have released their next champion roadmap which announced visual and possibly audio reworks for Ezreal, Nunu, Kayle and Morgana, as well as a completely new mage champion. The trio will also get kit reworks, with varying degrees.
This will be the final champion roadmap for 2018 and not all of the work from it will be completed before the year's end, as Kayle and Morgana's reworks are scheduled for release in early 2019.
Nunu seems to be the first on the rework list as Riot Games will attempt to make his kit up to date while keeping a whimsical theme. Currently, they are attempting to keep Absolute Zero's functionality similar to what we have on live servers, but will likely give him a way to activate it at maximum charge via some other ability.
Consume will also stay similar since it's his second iconic ability, but Ice Blast and Blood Boil will likely get more extensive changes. Meanwhile, they didn't specifically state whether Nunu and/ or Willump will receive any aesthetic changes.
Ezreal will however, as Riot Games want to make him seem like he doesn't belong in a museum. He is slated for extensive visual and audio updates, with the picture of his gauntlet on top of the article serving as a teaser of things to come for the prodigal explorer. Ezreal's kit will not undergo drastic adjustment though, as only his W is a subject of change.
Kayle and Morgana will get updated in a single package apparently. They both seem to be targets for visual and possibly audio updates as Riot have stated they want them to fit with a "new theme that binds their narratives together". Gameplay-wise, Morgana's kit will stay as it is for the most part, with slight adjustments to her passive and W, while Kayle will get massive-but-not-really changes that will preserve her hybrid melee-ranged playstyle.
Finally, Riot Games have announced a new champion that will be a "colourful mage" that should be officially teased and announced sooner rather than later. You can check Riot Games' full thoughts on their official blog post.