Simons has been out of day-to-day management for quite some time. He was succeeded by co-CEOs who were then themselves succeeded, IIRC. (These are my recollections from reading The Man Who Solved the Market). Apparently his management style was always pretty hands off and they operated multiple successful quant strategies that were led by others. Their Medallion fund returned 22% after (huge) fees in 2022 according to the WSJ. [1] That's the employee only fund that has blown the doors off for 30+ years. They do have a few other funds that manage much more $ and manage external money that have never performed at Medallion's level. In other words, it seems like succession will not be a major risk for them in the near term.

[1] https://www.wsj.com/articles/big-hedge-funds-are-top-perform...