I got the very same email last month after we booked a stay at the moderate resort, POR, which we like. The same "Special Offer" was even listed under My Plans when I signed on to
MDE. But it turned out to be nothing more than a listing for more deluxe resort offers that were already showing as available under the Special Offers link for the very same dates. They were all the same, & nothing new.
But here is the really odd part, and maybe something useful for others to know.
The only more deluxe (& expensive) place we personally wanted to stay was GF, but there was absolutely no availability showing at the GF for the 5 days we already planned to go regardless of how much I searched. But then I opened the Special Offers "check availability" link on Disney's web site one last time. It auto loaded for 6 days after I put in our start date. So for reasons I can't explain, I let it search that way. And surprisingly availability was now showing up for GF.

When I repeated that search with the 1-day earlier departure date for a 5 day stay, all GF availability disappeared. So I figured oh what the heck, and called Disney's reservations phone number. After explaining what I experienced online, I asked if they were showing the GF being available for 6 days with our same start date, could I still get that resort there even though we would be leaving a day sooner. After putting me on hold for a moment to see if that was possible, they came back and said "Yes." I've never had anything like this ever happen before. And yes, we are now staying at the GF for the very same dates we originally planned to be at the POR .... thanks to some of Mickey's magic.