Extending powerapps UI with custom code

Are there any plans to let devs add custom controls to powerapps?  I've been using spfx and it works great. I can be way more productive in powerapps though {once i figure it all out). But there will be times when we need some kind of custom UI. 

I can implement custom logic using azure functions. Will I be able, someday, to implement custom UI  components using SPFX or some other tool?