there was some talk just before the 1ghz upgrades came out that new dual upgrades were in the pipeline as well.
i think i read this at insanely-great.com but they are a bitch to search so i dont know if you can dig up the article.
upgrades have been stuck at 500mhz for awhile but these new 1ghz upgrades were supposed to usher in a new set of upgrades including some high powered duals. the 1 ghz have arrived but who knows what happened to the duals. hopefully it wasnt all rumors. id love to see someone frop a dual 1ghz in their cube.