Next year could transform Rivian's entire business.Rivian Automotive (RIVN -1.84%) stock trades at a sizable discount to electric-vehicle (EV) competitors like Tesla and Lucid Group. That discount is due to the company's lackluster growth rates in recent quarters. But looking ahead to 2026, Rivian's growth rates should skyrocket. And there's one major reason for this impending growth spurt.Why does Rivian trade at a discount to Lucid Group and Tesla?According to many valuation metrics, Rivian trades at a si ...