I don’t foresee AoE on xCloud if xCloud means this type of setup:
… or even just having to do all the controls with your fingers tapping, swiping, and pinching the screen.
And there’s not ever been any announcement saying AoE would be on xCloud that I’m aware of. So, to answer your question, do we know if AoE2:DE will be available on xCloud? I’d have to respond with, “No, we don’t know.”
AoE2:DE would be a nightmare to play on a cell phone. I think what you’d want is some “AoE2:Lite” being made instead; where all the mechanics are abbreviated broad strokes, and the game is just a macro shell of AoE2:DE.