This change boils down to a change of label (and maybe salary), not necessarily a change of role or activity. As a technical communicator, my friend is already well experienced in usability: usability & human factors professional is one of the jobs that technical communicators do.
The short answer is (maybe)...
But in real life that short answer is at best a gross generalization, at worst a lie.
For example: if a tech writer is called in early in the product development process, he or she can contribute a great deal of UX expertise, thus saving many problems down the track. The more a product can be used instinctively, the less it needs to be explained.
So a technical writer, by acting as a UX professional alongside designers, can lessen the technical writer's load down the track. Why? Because fewer words will be needed. After all, on the whole, the more we explain, the less people understand and and the less they remember.
If you have read this far and are saying 'Waaaaa?', no surprise. Angels are dancing on pin-heads here! Anyone wanting to steer technical writing career towards a usability career should just take some practical steps, as my friend is already doing: