I don't think Steam supports Android version, but I'm not gonna stop releasing it for Android.
Steam doesn't support Android as a platform.
It's possible they'd be OK with you putting up the Android version as a free-for-purchasers downloadable extra (as some games do with soundtracks, art, etc), but I suspect they'll say no. I've never seen a game on steam do that, and I doubt I'm the first person to think of it. Plus I've already thought of a couple of problems with it, so yeah, I don't think that's happening.