Mobile Legends recently conducted a survey about which JuJutsu Kaisen character fans would like to see in the game but it looks like that collaboration will never happen!
Another multiplayer game, Onmyoji has already announced collaboration with JuJutsu Kaisen, which makes a collab between Mobile Legends & JuJutsu Kaisen less likely.
Onmyoji already has collaborations with big animes like Bleach, InuYasha and Kimetsu no Yaiba (Demon Slayer) and now with Jujutsu Kaisen.
This does not necessarily prevent Mobile Legends from collaborating with Jujutsu Kaisen, but it also hinders possible contracts with Moonton, as well as Bleach that shares space between Onmyoji and Arena of Valor can also occur with Jujutsu Kaisen, the difference being the format in which content is released where generally one game holds the right to cast the character as a hero while another as a skin.