Buffett may still be chairman, but Berkshire's next big deal (or big buyback) will likely have Greg Abel's fingerprints on it.Famed investor Warren Buffett spent six decades turning Berkshire Hathaway (BRK.B 1.15%)(BRK.A 1.42%) into something rare: a collection of durable businesses tied together by one central job -- capital allocation.Now that Buffett is no longer CEO, that job is moving into Greg Abel's hands. And Abel will undoubtedly be under the microscope, because Berkshire's next decade of returns w ...