While I don't plan to do that, there are others out there, including open source options, especially developed and expanded in the more than 10 years since I built REXPaint because the relatively few options that existed back then at least were pretty bare bones and I needed something more suited to my own needs, and with more features. Nowadays you can find many more with different feature sets, design sensibilities, architectures, and audiences.
I'm pretty sure there will be a REXPaint 2.0 at some point, for which I have a lot of big plans, but that will definitely still not include much better file browsing or management, either
(feels like a waste of dev time to do something like that which is already solved, and not especially relevant to an image editor, so my focus is on new features that enable creation of cool images)