If they had "great performance reviews" and spent years working on IBM specific technologies, their skills may not be in high demand.

On the other hand, if they had skills relevant to the larger market, they wouldn't be dependent on their job for their livelihood but their skillset.

There are plenty of companies looking for developers. I know in my neck of the woods, there are plenty of job openings for the right skill set. It took me less than 10 days to find a job the last time I looked and I didn't hide that I graduated college in the mid 90s.