I used to own a bricks and mortar quilt store. Because of inventory issues and needing to clear out for the new fabric ordered, we used to mark the Christmas fabric down the week before Christmas because it would still sell then. Not much of a market for Christmas fabric after Christmas.
I have gone into stores in March through May looking for Christmas fabric. It was never there. I know that the fabric companies start making it available around that time. I guess most hold off getting it into their stores until June or July. I guess it is an inventory thing or needing to focus on selling the spring summer lines.