I don't believe they will be releasing any numbers :3 my only hope is that they do a bit more into marketing the app because most of my friends have never heard of it until I introduced them to it :3 (paid ads maybe?)
I am also interested to learn what the devs plan for the future and the release schedule of planned characters
People will spend money for strong or favorite characters but I feel some of their issues in getting people to spend more money is having the original (and free rotation characters) simply far stronger and more powerful than the rarer characters that are more difficult to obtain. I wish they would introduce aesthetically pleasing and powerful characters that are even in terms of power to the "original" characters you can find in prize fights.
I, for one, am super excited to see characters such as Ultraviolet and Brain Freeze make it into the game!