I feel like this discussion wouldn't be getting so much traction if it was easier to learn the differences between specific versions. Today there's enough resources out there to learn about rails and/or the differences between versions and/or 'the right way' of doing things, but it's scavenger hunt meets jigsaw puzzle. Currently, if you don't follow the Rails evolution regularly, going out there and catch up with it can be intimidating for some.

There's a need for a central Rails reference that makes this task trivial. Maybe a document with some sort of interactive diff functionality that allows to see specific version differences side by side in a friendly manner. Some system that doesn't force the writers to re-think a full document for every version, that can evolve without erasing older information, and that assists the reader by showing specific chunks of information that she should read in order to catch up to the specific version she is aiming for. Getting this started is a non-trivial task, but it seems like there's enough energy, innovation and attention to detail surrounding Rails to solve this problem.