Greg Abel is set to take over as CEO of Berkshire Hathaway at the end of the year.The end of the year is fast approaching, and for Berkshire Hathaway (BRK.A +0.93%)(BRK.B +0.85%) shareholders, that means one important thing: Their company will have a new CEO. Warren Buffett, who has been at the helm of Berkshire for decades, is finally retiring. The billionaire investor has enjoyed a remarkably successful career, which will finally draw to a close.Losing its visionary and long-term leader will obviously be ...