I agree that a lot of the churn is each generation (a generation here seeming to be about a year) of tools learning from and building upon the former. Obviously the churn is continuing since developers realize that the tools are quite "there" yet. My hope is that some year we will finally reach "there" (not perfection, but highly good enough) and the churn will slow down to the point that perhaps the generation time period will stretch out to five years or so.