What's the concurrency story in middleman?

Can parts (or all) of a middleman build be done concurrently? Is this an option? Looking into possibly building on top of middleman, but with a large site that’s pulling in lots of data, doing a bunch of IO, and also a fair bit of processing I’d love to be able to do some of these steps concurrently.

There’s been a discussion and draft implementation of it:

  • Parallel building (#799)
  • Parallelize build steps (#1113)

Work on this was postponed until Middleman v4 and might be ready for someone to resume now.

What’s the latest on this? I’m loving middleman, but the generation time is a drag. Is there anything I can do to move this forward? Test or port an existing patch? Start implementing a basic version from scratch?