Looks like quite a lot to take in, where should we start? - are there updated tutorials, upgrade guide etc?
And the detailed change list: https://github.com/d3/d3/blob/master/CHANGES.md
I will update my tutorials and examples (and probably write new tutorials) in the near future, and I expect others will, too. But as I now have thousands of examples, I didn’t want to hold the release on updating all of them. My newer examples use 4.0 already, and I’ll be going through the others in the coming weeks.
I know many tutorials reference your examples and it might create more confusion if they are updated in place.
I suppose it depends on how much you want to keep supporting v3, but I'd argue its worth keeping the old knowledge base intact for a while.