I said it before and will say it again, this is a good move by canon for all of us. the mkii is a very good camera, but no way is it still $2500 good, not in the face of the mkiii and the d800. And yes, it does correct the used market too. used mkii's will be able to drop to a more reasonable price ($1400-1800). I believe the used market was artificially high do to the combination of the new price going up, and people holding onto their bodies (scarcity = supply low and demand high).
In a way too, it may not lead to current mkii owners getting as much as they thought they'd get on their mkii (again, artificially high resale prices of $1900-2200) - but - it will lead to a quicker sale!
I'm sure there are many out there in a similar place as me, on a 7d and looking to move to FF but watching the market and waiting for the right time. I came close to pulling the trigger on a used mkii a few times these past 2 months, but just couldn't bring myself to spend 2K on a used body with who knows how many shutter actuation on it. At that point, manswell just wait and save and get the mkiii. So while you may be like, oh crap, there goes the resale value, once the market is flooded with mkii's, only the highest quality used bodies will be tagged at $1900 - and sorry, if you've had your mkii for 3 years and used it heavily, its not worth $1900...
Now things may change though, with the new price being corrected down to $2100, and the mkiii about to be released - we should see more mkii's used for a reasonable price