I honestly didn't think about doing that until you mentioned it. It might be possible, but I'd definitely have to check with itch.io (I'd have a tier that is basically a pre-order and doesn't give any rewards now). I'll think about it some more, but realistically, I won't be doing anything about until the Steam Game Festival ends.
The safest best right now is to simply wishlist the game on Steam to be reminded of it at release. Once it releases, it will be available both there and on itch.io, so you can buy on either site.
Either way, thanks for being so invested that you're willing to part with your money now for a game you'll only get later! :)