I would love to buy the standard editon of Shadow Warrior 2 now and buy the delux edition later but I do not see an option to upgrade from standard to deluxe. If I want the soundtrack would I have to skip the standard edition and get the deluxe edition right away?

Yep. You have to buy the Deluxe Edition unless they decide to add an upgrade. Specifically asked about being able to upgrade after I had accidentally bought the regular version and they told me I couldn't pay the difference. Had to get a refund and then buy the Deluxe.

True, I read the same a time ago. And I think you could ask for the loyalty discount too.

I hope they do add one. I wasn't aware of an deluxe edition till after I start playing it.

You don't get that much, just a golden skin for mp7 weapon, katana, and clothes. Plus soundtrack and artbook

Judging by how the installers are, I'd be surprised if they didn't do one at some point.

Currently, the pre-order stuff is a separate installer to the main game.