So will the game be treated as canon?
I am assuming so;
The storyline crosses paths with the action that occurred during the first two seasons of the series.
While at the San Diego Comic-Con International last summer, Lost executive producers Damon Lindelof and Carlton Cuse said that "The sense of adventure and suspense that we strive for in the show is also captured in the Lost video game."
In a press release sent last July, Ubisoft revealed that players will play a never-seen-on-the-show passenger of Oceanic Flight 815 who survived the crash. Players will have to face the same demons that hit the characters on the show (a dark past, redemption, being stuck on an island, etc.) while trying to solve puzzles, face the smoke monster, fight enemies, make alliances, and much more in order to stay alive. The game features the main characters and locations.