T-shaped is a good way to go, career-wise. Being a generalist with deep knowledge in some specific area (in my case video processing/computer vision/firmware) turns out to be very marketable if you apply to places looking for the area you've got deep knowledge in. The fact that you're ALSO a good generalist make you a very attractive candidate.

If you can, look at new jobs/companies as opportunities to get deep experience in a new area since over time, stuff you're good at now will sometimes go away.