It has been a long while since a major release of webmentions, and it is not the end of the plans we have. It is merely the first step.
The challenge as I see it, and the reason I don't use them, is that retail themes do not support microformat 2. Without microformat 2 support and semantic markup, the IndieWeb tools and technologies such as Webmention are pointless. Until the microformat 2 issue is resolved, I don't see any point in doing the work to support blocks.
IndieWebCamp NYC 2019 is a two-day maker event for creating and/or improving your personal website. All levels welcome! One of several 2019 IndieWebCamps and the seventh IndieWebCamp in NYC!