It's not sakura.... That Drop of ink is clearly ontop of the mountain sides while sakura was down in the rugged terrain with naruto and sasuke. Sakura wouldn't move so far away so quickly for just a split second.
It's either just a part of the cliff or Sakura. In the version I read, it didn't look like a person at all. Also, Kishi would never ever introduce a new and/or important character's entry like that.
Dude it is Sakura... Read the chapter and look at the panels leading to this and you will see only Naruto and Kakashi standing next to Obito.. Sakura is no where near them so the image you are looking at is Sakura she has no chakra and is useless in this current situation.. She has to take a back seat.
Laughing at people saying it cant be sakura lol... There is a 90% chance it is her as we can see that she isnt standing near obito and naruto. It is possible, but extremely unlikely that its a new character, especcially considering naruto or black zetsu would sense them.