He says, "Where I am taking you, there is no return." Then flashforward Felicity says, "I've been waiting a long time to see him. I'm ready.."
Oliver doesn't die. He just got forced into another part of the multiverse. Calling it now.
Ah, if it's the flash forward Felicity, then that makes more sense. I was thinking it was the current Felicity because it was so soon after the scene when Oliver left, which threw me off. That clears it up. Good recap.