I don't know any Carolyns, only Carolines.
I love the sound of
Carolyn, but I despise the spelling. BtN says that
Caroline may be pronounce the same as
Carolyn. So, I can see some people doing it. I personally do not.
Carolyn ends with a -lin sound for me and
Caroline ends in a -line sound.
I don't really think it's dated. I think it's close relationship to
Caroline keeps it youthful. Though, I'm sure there are quite a few people who feel the opposite!