Is Grimmjow Jaegerjaquez alive?
Ok, I found the omake that mentions Grimmjow: 



In the bottom-right corner, it reads:


  Q: Will there be characters that appear in the role of a friend? 
  
  Kubo: Ulquiorra has already turned to ash. Grimmjow might become a friend...


So yes, Grimmjow is alive.