To be honest - *most* people will not need more than 8mp, so 10m/12mp cameras are really moot as far as I'm concerned. Squeezing these extra megapixels onto the same size sensor will result in more noise, despite innovations that Canon might make etc. The 1D Mark II/n sensor is a 1.3x crop, this will mean larger pixels, thus less noise, courtesy of science. Digic III might be better, it's hard to say how much of an influence this would have on things.
You haven't mentioned what type of shots you take, if you need large/fast buffer, solid build quality of a 1 series camera, the improved AF of a 1 series camera, weather sealing of a 1 series camera, etc. Also take into account that as a general rule, a 1 series shutter assembly will last a LOT longer than a 40D's, which probably means savings in repairs etc.
Live view is nifty I do admit, and by all accounts the IQ on the 40D seems quite good, including noise performances at higher ISO ratings. The AF is improved over earlier Canon prosumer models as well, which is a nice bonus. I never really honestly rated the AF systems on the 20D/30D.
It's your money, and your choice, you have a tough decision to make.
Dave