If "Devin" randomly decides to push ransomware to the production server 0.01% of the time -- or just fail in one out of a billion different ways that would be catastrophic for the people that employ him, then "he" will need constant babysitting and end up as little more than a useful tool for a human engineer to supervise. Imagine how vulnerable your company becomes when you employ the same army of AI devs as every other corp, and someone finds a exploit to get him to babble API keys or cause him to produce insecure code that can then be exploited by a human. Imagine how large the potential attack surface is for a technology that we don't quite understand yet. Imagine how many corporate MBAs will push this hard only to have it backfire gloriously in their faces.
P(Devin replacing a good software engineer who writes anything more interesting than boilerplate) = P(Bangalore uber drivers getting replaced by Elongated Muskrat's self-driving cars that will come out in 2020...no wait, 2022, no sorry, uhh, 2027?) Not saying it won't happen but reports of the demise of people's jobs are greatly exaggerated and premature.