1. Warren Buffett retires, prompting major leadership changes at Berkshire Hathaway. 2. Todd Combs leaves for JPMorgan; Geico's Nancy Pierce replaces him as CEO. 3. Greg Abel set to take over as CEO; expected management transitions ahead. 4. Leadership shake-up may lead to more departures as Buffett's era ends. 5. Berkshire hires its first general counsel, Michael O'Sullivan, for modernization.