Wollay and most software development he does is intermittent at best. The Cube World community went 6 years without an update. He will occasionally (every few years) post screenshots and teasers on social media, but it seems very clear that development of his projects is whimsical. I don't think anyone at this point would be surprised if he tweeted out tomorrow that he's done developing Cube World.

It also seems that Plasma was never actually sold. It was a preview that just required a free signup.