Well a bunch of AI researchers are not gonna say AI is gonna kill us is 5 years. If they did, they would lose their jobs.

If a self-improving AI could exist, it would be exponential in its self-improvement. So just like a supercritical nuclear reactor, it could conceivably go from undetectable level of activity to supreme intelligence within a very short span of time.

It would be like the nuclear engineer at chernobyl saying "is only 100MW comrade, is of not problem"