User blog comment:Uraharattack/Grimmjow or Gantenbainne? Maybe both?/@comment-10554972-20130730025528/@comment-11051098-20130730032336

It can only be Grimmjow. Ichigo doesn't know anyone else in Hueco Mundo which is still alive. And he's the only one who would talk to Ichigo in such a manner.

Regarding Ashido Kano - since he's not in the manga, it would be strange to introduce him now, he would come straight out of nowhere. Kubo would in that case have to do something "extra" to introduce him in the manga, something that could just be cut short in a possibe animation of this arc.