I suspect that the more intricate/technical the skill is, plus the bigger the ROI of that extra technical know-how then the more likely a role will exist for this. So for example, if any person can get the same results as a dedicated prompt eng, then the less likely a prompt engineer role will exist. Also, if the prompt eng can get very different (and higher quality results) than any person, but the results are not that profitable, then less likely a prompt engineer roles will exist.

Bonus points for the likelihood of a dedicated prompt engineer role if the engineer can apply their wizardry across many aspects of the company. This kind of reminds me of the OSS (operational systems support) team I used to be part of, and still miss. In this team we applied mostly custom software solutions to any team that needed it. We worked hard to find customers within the company to earn our keep, else we would get laid off at the next convenient chance. I imagine prompt engineers, if given the chance, should work hard to find value and not just wait for the work to come to them.