As announced before a new project is under development. 'Firesinging' is an effort to return Age of Empires Online by building a public, open source server emulation. Primarily the focus is on offline single player with original gameplay, so you don't depend on Microsoft or someone else to host a server and can loose game progress at some point. View the video below or visit the project YouTube.
You can also follow development soon by visiting https://github.com/firesinging.
Please note this isn't an AOEO4EVER.net project and we cannot provide more information at this point.