A future Steam release is in the cards, but I love Itch and wanted to prioritize them. There's also a fair bit of extra work involved in a Steam release, like adding achievements, cards, and other stuff. I sincerely wasn't expecting the game to do as well as it did, and now that it's getting attention, I'm glad to have a smaller audience while I fix the bugs people are finding and working on the features people really want.
So! Itch is Mixolumia's home for now, and we'll see about a slow rollout to other platforms.