Short term, yes. Michael was not offing Fredo in Cuba.

Long term, possibly but not certainly. Would Fredo have volunteered more information than he did later at the boathouse? His emotions may have been more piqued, allowing for more of a purging of the soul so to speak, which could have saved his life.

My instincts tell me that he would have been no more forthcoming, so his fate would have been the same regardless.