I don't think the price of brand-name 300/2.8, the new 100-400 or the Sigma are going down.
Reading the reports, it seems that AI Servo on this lens only works well with newer cameras (i.e. 70D, 6D, 5D3, 1Dx) and, maybe except for the 1Dx, only with the central points.
It's not clear at this point if it is a hardware (camera) or software (lens firmware) problem. We all hope that it is the second, especially if it is the reason why availability in Europe seems zero as of yet.