All signs are pointing to a new Metro game that will be coming in 2017 according to the timeline on official website for the Metro 2035 novel.
Dmitry Glukhovsky, the author for the novels, released the original Metro 2033 novel in 2007 with the sequel, Metro 2034 in 2009. The third and final book, Metro 2035, is scheduled to release on December 10.
The timeline on the Metro website specifically states that “It all adds up to something. Where the books end their story, the game will pick it up. An area of great discoveries lies ahead…”