You can never assume that anything having to do with your credit report will be done automatically. Credit reporting agencies are private companies, and their income comes from the businesses that use them to screen customers; they have absolutely no responsibility to individual people other than giving you the one free annual credit report required by law. They have no interest in getting things right except insofar as it impacts their bottom line. And your name change doesn't.
It's vaguely possible that some people have seen their names automatically changed. But if you actually want it done in a timely manner, you're going to have to file the name change with the credit reporting agencies yourself.
As for whether the old name will be removed completely: zi don't know. I wouldn't bet on it, but it's possible.