In my field (Technology, Networking, InfoSec), I would always leave on good terms/politely.
So many times, our company was bought/sold, and you end up working for or with the same people (who have left) many times over.
I see it all the time. Ive been here 18 years and wont leave until I'm done in this field, or they ask me to, so i don't worry about it.
I only plan on 9 more years and getting out at (OLD) age 60...