I have done that but a little bit different in your case. I cancelled the Delta Platinum Skymiles card and got the Gold Business (not Skymiles) for 2011 back in April or May of this year. When I got the DL email about the DL Plat SM card for 15K MQMs (5K on first use and 10K more after 1500 spend in 3 months, $100 back after DL spend within 6 monts, annual fee $150), Iapplied, got approved, got my 5K MQMs after first spend. You may have to wait a little bit to apply but make sure you use early enough in the year that the first 5K MQMs will be credited before 12/31/11. DL Skymiles Platinum is a good deal because if you do all that is required of you and get the $100 credit, you are essentially paying $50 for 15000 MQMs, or 1/3 cent per MQM, much better than a mileage run.