Absolutely- Sonny would have let Michael get whacked

But I think it was more so to do with the fact higher ups thought he wasn't sharing enough

It's quite funny how Michael talked himself out of being hit by bringing up more potential deals he had lined up/ and how the bosses would make even more money with him alive.

These greaseballs are so damn greedy lol, that's one reason why Black Pete was deathly protected by Vincent.

As for Michael and Sonny making a powerplay, hmm interesting. Perhaps they could have considering Sonny's stature and Michael's money

But there was a lot of Persico loyalists not to mention blood relatives

It's not as easy as clipping Big Paulie for example and only having to
worry about his most loyal underling Bilotti or his one mobbed up dress making nephew blinkey