The post-Warren Buffett era for Berkshire Hathaway will look quite different.For the better part of the last six decades, Warren Buffett has exemplified investing excellence. Though he hasn't outrun the benchmark S&P 500 (^GSPC 0.44%) in each of his 60 years as CEO of Berkshire Hathaway (BRK.A 0.20%) (BRK.B 0.24%), he's crushed Wall Street's major stock index on a cumulative basis, with a nearly 6,000,000% aggregate return for his company's Class A shares (BRK.A) compared to a roughly 44,000% total return, ...