The official Metro: Last Light Twitter account has posted up a screenshot of the underside of a rocket, and it’s very clearly (judging by the hand at the bottom of the screen) a Metro screenshot.
I don’t know whether said rocket is a nuclear missile, or a space shuttle, or what. I’m afraid I know slightly less about rocketry than I do about football. One way or the other, though, it’s a Metro thing, and judging by the accompanying text “What’s this, more Metro coming…?” it’s not something that’s currently out.
We know of two more pieces of DLC coming for Metro: Last Light. Next up is the Developer Pack, featuring a shooting gallery, an AI Arena, and the I’m-totally-not-playing-that Spider’s Nest mission. The final piece announced is be the Chronicles Pack, giving you the chance to play as Pavel, Khan, and Anna as they proceed through their own little side stories.
Could this be a shot from one of those? It’s theoretically possible that one of those three characters could wind up coming across a discarded rocket, but it’s hard to say for sure. I’m just hoping it’s not the Spider’s Nest mission, because that screenshot shows sufficiently high ceilings that the eight-legged nightmare machines could drop down from anywhere.