As a Swift compiler developer myself, it's hard to commit to doing this regularly, because it takes significant effort to distill compiler-implementation work down into digestible content, and of course work-in-progress can change significantly. Technical blog posts on swift.org require a lot of effort.
I feel like the Swift weekly brief does a decent job of collecting what's going on and pulling out the interesting tidbits from GitHub, Twitter, the forums, and other Swift gathering places. I'm sure they'd appreciate more help keeping the community informed!
All that said, I wrote up something about progress on the function builders implementation that's probably the kind of thing you're looking for.
Doug