To be honest, I think Nyotengu should be the last character. These new characters have literally little to no back story at this point. Team Ninja would be better off saving new characters for DOA6 at this point. Also, unless they want to take the random dice away from character select, where would the new character go? Even though it might not matter to some, I like having the random function and I like a symmetrical character select screen. Also, my other reason for TN to not introduce another new character is petty. I've bought majority of the costume DLC thus far and with new characters means more money on DLC that I want to spend, because I just like having all the costumes. Yes, I know I don't HAVE to buy all the costumes, but it's just something about me having a complete package.
That is also why I hope why a complete edition package of DOA5U doesn't get released, UNLESS, it's just a package with the three DLC characters included from the start and the original DOA5 DLC costumes for all the characters unlocked from the start as well. I don't see Team Ninja making a complete edition with ALL the DLC unlocked from the start. That would alienate fans who bought all the DLC thus far. Just my take on this.