Ohhh, Acacia. You'll definitely have to wait for a new rainbow ticket promo then, and they don't exactly come around too often. The anniversary promo was the previous one (2 months ago).

Golden Week may have one (last year's GW promo was also a 6* ticket promo), but it will still depend on the whim of the devs and the current promo is already a rainbow promo - devs appear to alternate between 6* and 5* promos...