I guess the knowledge that Roland has dissolved its arranger division and subsidiary Roland Europe has also deterred customers from investing in a Roland arranger, in addition to terrible marketing and video presentations. If you look at sales of the BK-7m (released in 2011), there are over 20 (positive) customer reviews at Thomann. I really hope Roland will develop an updated module some time. The BK-9 has a complete BK-7m and many more sounds on board.
However, it is also Roland's own fault not sticking to their announcements to release expansion tones for the BK-9 and not providing any updates since October 2013.