Most people don't need the Xeons that's in the Mac Pros and definitely not for 2700$. Mac Pros are overkill for majority of people and iMac is nearly perfect for us except it could use more stuff in it, which is why this topic was created, to see what people want in their iMac.
There are cheap quad processors that fits iMac's market. Granted, most people probably still don't need quad cores but Intel is practically getting rid of the dualcore and replacing it with quadcore at same price point.
If Apple could make it easy to replace HDs and go for upgradable graphic cards, it would sell craploads more units than ever in their history.
Apple can produce Mac Pros at cheaper prices by replacing the Xeons with the consumer-graded CPUs like quadcore core duo or the Core i5/i7. Just dropping the price to 1500-2000$ will be enough to satisfy people who are searching for the "xMac".
It has nothing to do with drivers, Apple could develop the drivers anytime they want. The drivers are useless if you have nothing to use it with. They have to wait for the USB 3.0 host controllers to be developed and tested and than mass produce it. Once the controllers are ready, than the motherboard chipsets have to be developed with it built in so that Apple can use it in the next product line. Those all takes time.
