Career “Fork-in-the-Road”

I am faced with a decision in my career. A opportunity has been recently created for Unix administration and I am currently a NT/2000 administrator. I am interested in other NOSes, but I know if I take this opportunity I will not have much opportunity to continue administering NT systems. I know I could get proficient in Unix, but I don’t really want to let go of NT experience.

Any recommendations?