Since unity is c# I think maybe you phrased that opposite of what you meant?

Anyway, I work in an enterprise environment. We use both Java and .Net, and it largely depends on which group you're in. Neither Java nor .Net is going away anytime soon.

You really don't get to stick with just one thing in a developer career. Learn a little of everything, especially multiple paradigms, and specialize in a few related to the business you work for.

A key skill is adaptability, learning as you go. If you make yourself too specialized, you'll set yourself up for being laid off when your skills become obsolete. I have interviewed a few older IT people in that situation, only a few years from retirement.