I received a mail offer for their generic "Citi Platinum Select" Mastercard in Febuary 2012 and took it, approved with a limit of $1000. Exactly one year later, they upgraded me to their Diamond Preferred with a $2000 limit. I rarely used the card. Hope this helps.
At about 18 months they "upgraded" my Platinum Select MC to the Diamond Preferred World MC without me requesting. They just did it.