Question: Which of the bundled themes are being migrated? What about other themes on wordpress.org?

Answer: So far block versions of 2021, 2020 and 2019 are being developed in Theme-Experiments.

• There are over 8,000 themes on wordpress.org.
• Assume that new FSE versions of existing themes will be created.
• If only 2% of these themes were cloned that would be 160 new themes.
• But how many child themes are there?

References

• FSE themes
• Theme-experiments