I think the more logical question to ask is would Fredo have even betrayed Sonny...and the answer is probably not. Wasn't Santino the oldest son? Therefore there would not have been the jealousy and envy that was directed toward kid brother Michael at having been what Fredo percieved as 'stepped over.'

Had Sonny remained alive to one day run the family, things would've been completely different, there probably would've been virtually NO family after a few years, and therefore no one in their right mind would've even bothered to approach Fredo to 'help with negotiations'.

Fredo would not have had the opportunity to betray Sonny..and therefore Sonny would not have had to make the choice of having Fredo killed.

Also...I do not agree that Michaels motivation in having Fredo killed was "...whatever he had to in order to keep his power and position...". He had the power and position and allowing Fredo to live would not have changed that.

By doing away with Fredo, Michael was doing what he needed do to protect the Family. Not himself...the FAMILY.

Apple