The changes from 1.0 to 2.0 were bridged through extensive beta testing. If the changes are that intense for 3.0 to 4.0 and beta is not there, it is obvious to expect a couple of weeks of adding the changes for people to adjust.

It is irrelevant on whether or not that was the case for other games, cause 2.0 to 3.0 didnt introduce any fundamental changes to existing classes, therefore there was no need for that.

In the end, it all boils down to whether the changes will be that big or meaningful.