Account Migration has not begun. There will be an in game message when it's your turn to move. Do not fall for any third party websites that are telling you to migrate NOW. They're trying to steal your information.

When will bedrock be able to get the nether update on an ongoing world? I’ve had my survival world for over 4 years I even transferred it from my ps3 I don’t want to start a whole new world just because of that.