It appears to be Legends canon (not "Disney" canon)
Although the X-Wing miniatures game has had releases since the new canon rules took effect, such new content is still considered to be in Legends continuity.
An excellent example of this is the Imperial Raider expansion pack set to be released in 2015. The press release announcing the expansion pack describes how the Raider-class ship was created by Fantasy Flight Games for the miniatures game as a counterpart to the Tantive IV. The ship was designed in partnership with Lucasfilm, who of course decide what is part of the current continuity and was is part of Legends.
There are several signs that show that this ship is in Legends continuity, including references to locations and characters that are in Legends continuity (such as Kuat shipyards), and the BBY designation for the year, which is no longer used. The Wookieepedia article for the ship itself lists the Raider-class ship as being firmly in Legends continuity. As a reminder, this is despite being created in partnership with Lucasfilm and despite being released over a year after the new canon rules.
Other products in the line have similar indications that they are in the Legends continuity. This is corroborated by the fact that lists of works that are in the new canon do not list X-Wing, or Fantasy Flight's other miniatures game, Star Wars: Armada.
While Fantasy Flight Games has never released an official statement about the canonicity of the game, all signs point to it as not being part of the current continuity.