Warren Buffett is about to step down, but he's leaving behind a portfolio featuring several high-quality artificial intelligence (AI) stocks.Warren Buffett has served as Berkshire Hathaway's (BRK.A +1.01%)(BRK.B +0.85%) CEO since 1965, overseeing hundreds of acquisitions and stock purchases that have catapulted the conglomerate to a trillion-dollar valuation.Buffett plans to step down on Jan. 1, capping off a stellar 60-year run. Had you invested $1,000 in Berkshire stock when he took the helm, you'd be sit ...