I'll preface this post by saying the pre-purchase is a "hopefully" more than a "definitely". We're currently in the process of getting some stuff approved by Valve so it might take a little longer. If all goes to plan though, the game will be available for pre-purchase on Monday and will be unlockable on Tuesday.
We're also releasing a Launch Trailer tomorrow showing off some of the new levels, mechanics, etc. This time we haven't gone for the over-the-top glitchy look we had last time since a lot of people found it extremely hard to watch. See you then!