While reading Metro 2034 (finally out in english), I came across two important facts that lead me to believe that the "Redemption" ending is the cannon ending for Metro last Light.
In Metro 2034:
- Miller is confined to a wheelchair, missing both his legs.
- Artyom is married and living at Exhibition.
Granted, Miller doesn't say to whom Artyom's married, or that he has a kid, but since 2034 takes places "a year and a half" years after 2033 according to Miller, it's plenty of time for the events of Last Light to have happened. I think this is pretty compelling evidence that the Redemption ending is cannon. Of course this isn't 100% certain until Metro 2035 comes out, but the fact Miller's missing both legs in a wheelchair seems to strongly suggest it.
Thoughts on this?
EDIT: I finished the book and discovered 2 new points that further indicate that 2034 takes place after Last Light.
- Leonid, Moskvin's son who helps Artyom escape Korbut, has been exiled from the Red Line. In Last Light, he's still living there.
- Leonid dies at the end of 2034, so 2034 undoubtedly takes places after Last Light if Leonid is present in it.