With summer approaching, the struggle to reduce thermal noise becomes a challenge for the regular DSLR. If cooling mods were cheap and easy, then I think this would be a non event.
http://www.atscope.com.au/sbig/st4000xcmi.html - Same information, but AU pricing - A$4800. Probably comparable to a Ha modded, after marked cooled DSLR.
Possibly a limited edition, but would depend on demand and more importantly CCD chip availability. SBIG, like other high-end camera manufactures (FLI, Apogee, etc) secure a limited number of CCD's from manufactures such as Kodak, Marconi, SiTE, Fairchildimaging, etc. Despite what you may think, these guys don't have cameras sitting on their shelves already assembled waiting to be shipped to a customer. Assembly typically commences when you place an order, hence the sometimes longer then expected lead times. I waited 5 months for the STL11k (and that was quick compared to what I've heard from others). Of course, its worth the wait.