They'll probably need to add some type of new perk to the DL Platinum card to make up for loss of lounge access and loss of MQM boost, maybe a coupon for a flight discount or a couple drink tickets or an RDM boost after certain spending (I would imagine most people would cancel or downgrade to Gold). They're going to need to figure something out to incentivize spend on the DL Reserve, right now you would consider hitting those 30k spend thresholds for the MQM boost, but with the loss of rollover now you'd likely stop right when you hit enough for your desired year end status level. They may also offer promotions and offers from time to time like spend $5k in 90 days and get $2,000 bonus MQDs, something like that.