More D&D PDF's forthcoming?

[Felon]

I've been holding off on buying Sandstorm because I have so many books to tote that the seams on my backpack are bursting. WotC has released a handful of PDF books through DrivethruRPG, but I don't know of any plans to make Sandstorm available in that format. Then again, I don't monitor any other news outlets or blogs besides those at ENWorld. Anyone have any insights to share? Has WotC experienced any success with PDF sales?