http://www.pcgamer.com/age-of-empires-definitive-edition-gets-a-new-release-date/

Age of Empires: Definitive Edition, the remastered re-release of the 20-year-old RTS classic that was announced last summer, has been given an updated release date of February 20. Ahead of that, Xbox boss Larry "Major Nelson" Hryb said the multiplayer beta will be opened up so that everyone can get an idea of what it's all about before launch. 

The wording at majornelson.com is a little vague, saying that "we're also opening up the multiplayer beta to more players worldwide starting January 29 so everyone can get a taste of the game for free," which simultaneously suggests that a limited and unlimited number of beta applicants will be admitted. But a rep from developer Forgotten Empires said that everyone who has signed up for the beta will soon be receiving an invitation, and since the signup process is still open at ageofempires.com, you should get in if you give them your name.