Initially as a standalone game. There are however plans to bring Renegade X to Steam and/or Origin in the future.
Just as an idea: Why don't you put your game already on Steam Greenlight?! If you put it in by now there's a great chance your game can be one of the voted "greenlighted" games and be available on Steam by release!
Just have a look: http://steamcommunity.com/greenlight
Would be great to download it via Steam and get Updates automatically as well