We should do as long as we bought the retail as well as the download version, I'll be pissed if we don't, that's what we were pretty much promised. 
Apparently all orders of the retail from Stardock will get the collectors edition as long as 'stocks last' and as Stardock are a pretty far sighted company, I cant imagine they'd order too few copies to meet the pre-order demand (they'll probably be available for a while even for new buyers, I bet)
Edit: Kryo - Are pre-orders gaurenteed a collectors edition?