maybe do a 4 to 6 month demo update. but in the meantime just post information on what you're working on/adding at the moment. so you will basically update the demo 6 months from now but in a month post an update here somewhere just informing what's being worked. on that way if the update comes we can check it out and if we see what was said was added and was added decently that would be a big + regarding confidence in an indie developer.
thats just my take though. anyway goodluck with the project ill keep an eye on it if i remember it.