This is a wonderful post! Mainly because I saw this happening to me before I took steps to stop it.
It is very possible to become trapped in a skillset, even one that seems highly desirable. I've got friends who are thrilled at getting jobs in certain technical spaces and I hope for their sake that they get to do a bit of everything.
One of the best things I did at my last job was become a Scrum Master, mainly because it stretched some muscles I hadn't used for a while, and discovered I actually really like using.