Probably not. Our office here is not very well lit, but the few rooms that have decent lighting still have all the white computer parts as white as they probably could be.
I think modern plastics might not be as sensitive to sunlight and yellowing in general anymore anyway. My parents are both heavy smokers, yet their g81 keyboard is still pretty white, despite being in the room for over two years.
I dunno though, some plastic expert might reply with more helpful information!