Why would anyone have purchased a 9800 Pro over a 9700 Pro? The same thing seems to be happening here with the 9800 XT over the Pro... Seems to me as though the XTs will simply replace the Pros as the "enthusiast" part found on the shelfs alongside the non pro/xt boards.
And it may not sound like the cores are any more tweakable if they can get yeilds "only" at 412 or whatever. Hell, there's a reason the 9800 Pro was clocked at "only" 380MHz and the 9700 Pro "only" 325MHz. What does this mean? IT just means that those are the stable clocks they were able to obtain with those respective cores. Does it mean that they couldn't be over clocked higher than the yeilds ATI found suitable? No, it just means that at those yeilds they are certain they'll produce very few problematic batches where customers discover the default clock speed to be unstable. The cores are more mature and can probably be pushed further, but how much further is the question. Many "enthusiasts" didn't seem to have too much problems pushing the 9700 over 400MHz, the 9800 let users go a little higher, how much higher the XT will allow for might determine if it's "worth" it for 9800 Pro users to upgrade if they have the cash to burn.