First of all, I'd like to say that your game screenshots look very nice and I'm sure the game will be great. As far as having a demo and updating it as time goes on, I've done it myself several times. In fact my newest project (a Visual Novel adaptation of my e-book) is a demo that I'm updating over time. In different cases, because of how long the finished product will be, you have to have a demo you update over time and that's totally fine.
Viewing post in Uploading an unfinished demo
Thank you for your feedback. I'm now leaning more towards releasing an early demo and updating it till completion. One thing stops me though, my game is an adventure RPG. It will have replay value (emergent storytelling) but the demo won't really reach the point where you see too much of that. If I release a demo and people play through it, what motivation will they have to play through it again when it is updated? I can understand with a roguelike/lite game or some actiony game with fun combat mechanics, but story based games kind of burn themselves out after the first go. Thoughts?
First of all, I can understand your concern in regards to whether or not people would replay the demo. At the same time, though, it doesn't mean that people won't. In general, in regards to stories and story based games, there are people who read a story once and there are those who like to re-read the same story several times. Also, there are those who could replay the demo because they want to see what updates there are.
In general, what I would say is to work on your game until you get it to a point where you feel like you can upload a demo. After that, when you update things, you should write a devlog to let people know there are updates. Also, if you'd like, when the demo's available, you can write a post in threads having to do with Youtubers playing games and see if anyone is interested in playing the demo. Also, there have been times when Youtubers have replayed demos when there have been updates.