I dunno how many people are doing what I'm doing which is: Im waiting for the game to finish to give it an honest go. So you might still have some players at launch.
At the same time, I do support the idea of making a demo, especially for Steam. You are essentially forcing them to do what I am doing. PLay a bit, and savor it for the final release. Its not a bad thing by any means in my eyes, especially of you want to drive more people to Patreon (having troubles myself with that one >_> )
But Gluck with whatever option you go with.