Development can be tracked through the changelog or by browsing the commits.
The current tracker is what we got, no further development is planned to my knowledge, at least not until we get developers willing to work on it.
Natron is a node-based application, there are no plans to implement layers.
There are many videos on YouTube.
https://www.youtube.com/playlist?list=PLprXrT2oteICaZqvsrMQJHy4xIjkqqThH&fbclid=IwAR3g-jp9TcoJjirxKvjWILAEoAJmZMuE0GfRb7TCwjHV0Vsv1eeAXrl6WiE
Most (beginner) tutorials for Nuke will also apply for Natron.