BT2: 129How many "new" character slots are still available?
BT2(Wii PAL/JP): 135 (129 + Piccolo Daimao, Cyborg Tao, Pilaf machine, Pilaf's Combined robot, Generic Freeza Soldier, Appule)
BT3: Known 135 + 21 (New revealed forms) = 156
161 = total number of characters given by a Japanese magazine
161-156= 5.
So, there are 5 unknown characters. BTW, if Atari's statement about how there will be 20 new characters, not counting transformations, is to be believed, none of the 5 remaining slots are transformations (because there's no more space for an extra form in the total form count of 161), they're just individual characters.