I have had my Citi Diamond Preferred just over a year but needed to wait until the statement cut on 2/1/2016. I called today and they have made the change. It instantly reflected online.
I should have my new card in 10 days or less.
I look forward to using it as I almost never used the Diamond Preferred used it more as a door in with Citi. I did take advantage of a Balance Transfer offer and that just carried over to the card at the same terms.