I don't think its just a matter of price... I actually think that they really need to push the release date as far as possible in order to avoid infuriating current buyers. If a new lens is just out of the oven, you don't expect the company to put out in the market exactly what this should have been in about a year... every person that bought the mII will feel cheated, and that is not a good practice!!!
(Although Apple does it every time they put out a new product in the market almost identical to the previous one and everyone pays them... so what do I know really!
The other problem is that the mII release price was just too much!... it should have been $1900 not $2500, so now they have no price to ask for this one, as no one will pay $3000 for this one over the Tamron, even if its 3 times better. I really can't understand Canon current lens roadmap, save for the pancake 40!