I'm not sure what you mean by the properties and the cards won't merge and the card will be co-branded. I think there will just be one loyalty brand. I think ALL references to "Starwood" will disappear once the IT systems and loyalty programs merge, and the former Starwood brands (Westin, Sheraton, St Regis, etc) will just become additional brands under the Marriott umbrella (like Renaissance, Ritz-Carlton, Gaylord, etc). They'll come up with a single name for the loyalty program (Marriott Preferred Guest - MPG - maybe?) and all Marriott-owned brands (legacy Marriott plus legacy Starwood) will participate, so there will be no need to "co-brand" anything. Under this model, the resulting credit card(s) would just be the MPG Visa or MPG Amex and they would function identically at all of the brands. There would be no more StarPoints and Rewards Points. Both sets of points would be converted on some basis into a new "currency" (Preferred Rewards Points -??) that would be earned and redeemed the same across all properties. It's anyone's guess how they'll handle something like lifetime status, since if they allow both pools of points to count, the number of people in each tier will rise substantially and they may have to change the requirements or be content with a higher percentage lifetime Elite members across the board.
Thinking of it visually, I've posted the current brand banner from the bottom of Marriott.com below. Under a new consolidated program, I would expect the banner to change by eliminating the "The Ritz Carlton Rewards", "Marriott Rewards", and "SPG" logos on the left side, replacing them with the one logo for the new program (i.e. - MPG). The dividing line that they now have above the third row of logos would be eliminated as well, with the legacy Starwood brands being intermingled with the legacy Marriott brands. The lists seem to be roughly in order from high to low in market positioning, so St. Regis and Ritz would likely be listed next to each other in sequence, W would likely be in sequence somewhere around JW Marriott, Four Points would be down somewhere around Courtyard and Fairfield, and so forth.
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