There are multiple examples of this. Two that come to mind regarding Citi directly are Amex assuming Citi Hilton cards in 2018 and Citi assuming the Amex Costco cards in 2016.

If I had to guess, the no annual fee card would convert to the MileUp card. The Red would convert to the AAdvantage Platinum Select card. I don't know about the Blue or Silver since there aren't equivalent Citi products. It's possible that they'd offer options of changing from the Blue to the MileUp or AAdvantage Platinum Select cards and from the Silver to either the AAdvantage Platinum Select or AAdvantage Executive cards.