Call now and talk to retention. I called and simply stated that I had heard they were offering the new customer Sunday Ticket promotion to existing customers and asked very politely if "it was an option for me." He immediately came back and said I could have had it from day 1. No sell on free superfan though. I thanked him, hung up, and called to talk to the normal customer service line. He was aware of the free SF offer and looked it up just to be sure. He commented that my timing was great since the offer started Aug 1 and ENDS NOV 1.
Now of course each situation may be different so YMMV. I've been with D* for 3 years, been able to get this offer all 3 years, and am out of contract. I have 1 HR20, 1 R15, and a standard receiver. I already had the premier package (never downgraded after last year's offer) so in effect D* is actually giving me a $30 programming credit for 4 months AND free ST/SF.