Anyone could always change their name to anything they wanted, regardless of whether they were verified or not. But before, if an unverified user changed their name to Elon Musk, it'd be immediately obvious it wasn't the real Elon Musk, because there would be no blue check. And verified users had no motive to change their names to Elon Musk, because the reason they were verified is to post as themselves. Once the new "pay for blue check" system is operational, then people who want to impersonate somebody else just have to pay $8, get a blue check, and call themselves anything they want.