Donnie Yen confirms that Jedha is in the new canon where you get lightsaber crystals (he technically only referred to “resources” but I hardly see what else it could be). So there’s probably something to the fan speculations that Jedha will be the source for the crystals used in the Death Star canon, hence its importance to the plot.
http://www.starwarsnewsnet.com/2016/07/star-wars-weekly-social-buzz-15.html