Similar to Adobe XD functionality, a checkbox for containers or shapes that makes everything underneath it blurred.
I'm waiting too!
This is exactly what I want. I was recreating Twitter iOS app-like header, where the cover image becomes header background as you scroll, making the picture blurred at the same time.
This is the feature I have been waiting for since launch! All my sketch and XD designs have used background blurs in one way or another, although it is somewhat okay to translate a blurred out background into a still image layer, for the time being, there is no way to replicate background blurring dynamically :(