the UX group of the Structured Content Initiative is currently working on wireframes and a technical concept for dynamic grids. We hope to have a solution (either as an extension or maybe even in the core) until the feature freeze for TYPO3 v11.
Our Content Block Creation group has recently created an extension (currently still in alpha) for the Content Blocks registration API and keeps working on it. It will probably remain an extension for TYPO3 v11, but we hope to have it ready to be applied in real projects until then.
You can track our progress in our roadmap: https://typo3.org/community/teams/typo3-development/initiatives/structured-content/roadmap
We are also happy for anyone willing to contribute, e.g. by testing our stuff and giving feedback!