Kabuto told Tobi that he couldn't find Obito or shisui when preforming Edo and Tobi responded don't Push your luck.
Well he obviously couldn't locate Obito because he is alive (Tobi) so why couldn't he locate Shisui? This story won't end without one of the most powerful ninjas not making an apperance.. Shisui is the only shinobi Itachi looks up too and that's saying a lot. Itachi also compares narutos will of fire to Shisuis..
Do you guys and girls think Shisui is still out there in this story? He was never located.