Yao Zi will eventually obtain a human form in the far future, but it's not gonna be through spirit beast evolution but something else entirely.
Yao Zi was not very intelligent, cunning or skilled in a particular field, and neither was he blessed with any underlying overpowered cheats as all typical main protagonists have, but what he has is knowledge.
That Time I've Got Reincarnated As a Spirit Beast in a Douluo World