I don’t think the LLM is gonna do that great of a job with it for this reason, but still worth giving a shot. ChatGPT is a well trained coding chimp. You realistically could get a well trained chimp to start off a lot of projects and have people finish it. The fact that it can correct itself after you explain how it’s wrong is very powerful as well.
LLM isn’t gonna be useful for converting a single program from COBOL to Java, it is gonna be useful for converting many programs from COBOL to Java. I bet IBM is trying this on their own shit first before they try to sell it to customers, because language conversion software would be a HUGE but very boom based money.