Akali was updated and balanced several times since its rework in 2018 and 2020 will make no exception. Major changes are planned for two of her spells alongside patch 10.3 of League of Legends. The goal here is to rework skills rather than simply nerf her damage.
We can say, without a doubt, that this nerf is pretty massive. W - Twilight Shroud is the main tool of Akali: with this double nerf — the movement speed bonus and the fact that she can now be revealed — her ability to run from fights after diving in to assassinate a carry will be drastically reduced.
However, the real downside comes with the nerf of R - Perfect Execution. The R1 is now a targeting dash, meaning Akali won't be able to use it as an escape as easily as before. Moreover, the fact that R2's dash speed has also been nerfed will leave more room for people to escape with Flash or to react with a CC.
Reactions to this announcement were not long in coming. These nerfs were not well received by the community, many judging that Riot Games was simply killing the champion. Some even called for the return of the former Akali. Many players mentioned that the Rogue Assassin had already received too many nerfs and that the majority of players aren't able to successfully play this champion. Akali's winrate is 46.5% at the Diamond level (even lower in low Elo) and at the Master level and above, his victory rate rises to 55%. Undoubtedly, the nerf more would make her extremely difficult to play.
All these changes should be shipped to the PBE with cycle 10.3. The team is planning a longer testing phase in order to get maximum feedback from players and adjust these changes as needed.