As an example to illustrate me question consider this:
A mid-season trailer for season 2 of Star Wars Rebels was released recently and contains some pretty interesting things such as
a green crossguard lightsaber and 2 white lightsabers.
So seeing how Rebels is main canon, can the trailer be considered canon as well?
Or more generally, are trailers containing impending canon content to be considered canon?
Or is it inappropriate to cite trailers as evidence on this site?