i would assume that the current ptr build is what is going to be live for this patch though, so couldnt I/we take data for that as basically live. as i understand it there wont be anymore tweaks from ptr to live?
Things get tweaked between PTR Patches and what ultimately ends up on Live all the time; it's a useful point of reference, but it's by no means bulletproof. There's still at least another week before 4.01 as it is, things can, and probably will change in that time. Even once the patch is live, it's highly likely that there will be a number of tweaks, probably weekly, in that time between 4.01, 4.03 and Cataclysm itself.
As I recall, the month or so after Wrath included at least 3 major changes to most classes talent trees. It was 3.1 before things were considered 'stable'.