Mate I think that looking at how long it takes for a release to come only to add a couple new features and content, plus the fact that you're releasing a free version and taking away part of the new content you make that takes so long to be created and only putting it in a supporters version, the game will take years to be completed, and you will make less profit off of it.
Take for example games like Beat banger which even after taking long time for content to be released, their game gets posted here for free, but since people are enjoying the game they end up buying it or supporting it, and I think that's the way to make a game like yours successful. Does anyone else relate to this?