If you don't trust Sakamoto with Metroid, you should keep in mind that Konami didn't trust Igarashi with Castlevania anymore. IGA is also responsible for Lament of Innocence and Curse of Darkness, both of which hold similar notoriety with Castlevania fans as Other M does with Metroid fans.
As a fan of both series, I'd prefer if Igarashi not handle Metroid. I'm sure he could make a decent one then again, so can Sakamoto even if ridiculous Nintendo fans weirdly treat him like the town leper now. My concern with Igarashi taking over Metroid is that he got complacent with Castlevania to the point where he routinely reused sprites for previous games. After so many Metroidvania games, I wonder if he really has anything new to add to this style of game. He hasn't really tackled an original IP since Nano Breaker. Does anyone besides me even remember that game?