Are there any work-in-progress NIPs for image, audio or video posts?
Relays that could offer N amount of storage for N sats. Relays, or services, that could transcode audio/video for sats.
Discussion
The only thing I could find was a reference of "Future extensibility" in NIP -28 that reads: "We reserve event kinds 45-49 for other events related to chat, to potentially include new types of media (photo/video) (...)."
Also paid relays probably should have a bytes to sats rate for notes eventually as well, I would imagine.