Sure it's possible. You would need an IDE to SD interface converter inside the DMS. But due to the slots depth and the cost of retooling for only a slightly smaller DMS shell, an SD based DMS would most likely be the same size as what we have now.
And don't forget, with a 1GB SD card running around $75.00, with Phatnoises' typical 400 percent markup, and the added cost of the interface converter, that would make a 1GB SD based DMS cost $350.00 plus a huge shipping charge (which is probably mostly a 'handling' charge a.k.a. "the eBay scam").
In other words, it's never going to happen.