So how many costume DLCs are there going to be? Or was this one the last?
There will likely be at least three more. The Xbox 360 HDD file names for all of the DLC packs are labeled like below:
Add-on Name / File Name
Top Bunnies / Downloadable Content 1
Angels / Downloadable Content 2
Devils / Downloadable Content 3
Divas / Downloadable Content 4
Swimsuit Collection / Downloadable Content 5
First Time Pack / Downloadable Content 6
Round 2 Full Set / Downloadable Content 7
Round 3 Full Set / Downloadable Content 8
Round 5 Full Set / Downloadable Content 9
Christmas Set / Downloadable Content 13
Christmas Set 2 / Downloadable Content 14
Since they suddenly skipped from DLC 9 to DLC 13 for the Christmas sets, I take it that 10, 11, and 12 were delayed in order to get 13 and 14 out in time for Christmas. So we still have those three coming, but who knows if we'll get anymore after that.