As you said, we don't know anything yet. Though they seem to hint at it perhaps spanning the timeframes of all three predecessors, which would be an ambitious goal. Rise of Nations did that fairly well (and Empire Earth did the same thing), but the pacing was quite a bit different than Age of Empires.
I'm mildly interested; I played a ton of AoE III a decade ago, a somewhat lesser but still noteworthy amount of AoE II five years before that, and still play a handful of games of them a year. But I also rarely play RTS games in general these days. Also bummed that it's Windows 10-only; Microsoft has a habit over the past decade of limiting games they publish to the most recent version of Windows for (Windows) marketing rather than technical reasons, occasionally cratering the game's audience as a result (looking at you, Halo 2 for Windows Vista).
Edit: Although if they use DX12 in order to allow a scale that simply wouldn't be possible with DX11, it may be a justified decision. But a purely marketing decision wouldn't surprise me at all.