I doubt this will ever happen. It's all about complexity, and in case of text editors there are layers and layers of abstractions that often (for UX reasons) have to be integrated tightly. Trying to unpack all pieces into fully generic bring-your-own implementation is going to be a lot of work upfront and in maintenance, and complexity explosion.

I really like some technical aspects of Xi, but I view it as a typical wishlist project/technical showcase. In the meantime projects like kakoune, with much smaller scale but better focus, in shorter time, build ecosystems that can be a practical Vim alternative.