A lot of people rejoiced when it was announced that Taika Waititi would be back to direct a fourth Thor film, but some fans suddenly asked, "Wait, wasn't he going to direct an Akira movie?" As it turns out, Waititi had left the project so he could go back to the MCU.
According to The Hollywood Reporter, production for Akira had been pushed back because of some script issues, but after they were addressed, Waititi had jumped onto Thor, pushing the two productions too close together that one of the films had to be dropped. Guess which one got the ax.
If anything, WB is now waiting for Waititi to finish his work on Thor 4 before jumping back on Akira. If anything, it would be a safer bet to come back to an established franchise. Akira has been having a hard time trying to get off the ground, and if anything, we could be looking at another director change if WB should get impatient.
If you ask me, I didn't think that Waititi was the best choice to make Akira in the first place. Waititi shines with his smaller-scale stories like The Hunt for the Wilderpeople and What We Do in the Shadows, and Thor: Ragnarok, to me, was not his best work by a long shot. Perhaps he can improve on his technique by coming back to a familiar property with Thor, but for Akira, I would have preferred someone else.
Personally, I think they should pick someone whose done some solid CGI movies like Gareth Edwards (Godzilla, Rogue One: A Star Wars Story), or Denis Villeneuve (Blade Runner 2049, Arrival).
Then again, that's just one person's opinion.
For now, no release date has been set for Akira.
See Also: Thor 4: Ragnarok's Taika Waititi Returning to Write and Direct