i get what your saying cos naruto, sakura and sasuke are like chibi versions of the sannin but naruto only managed to learn it cos jiraya and him were close as a tree and bark, sasuke wasn't close ot oro at all and tsunade probs only views sakura as a student.
so im not all that sure if sakura will get anything....
which means imo she's staying usless haha
The answer is we don't.But the last chapter definitely hinted at the fact that Slugs are the last Sages.Throw in the fact that both Jiraiya and Orochimaru had sage modes that had to do with their summons(Dragon, Toad) and in only seems logical that the last place Kabuto mention is a where the slug sages live(Humid Bone Forest).Just base on facts, Slugs live in humid places.This is all speculation though.
You're forgetting that in order to be a sage you need large reserves of chakra, which Sakura doesn't have. Very few characters do at the moment. I'd expect either Tsunade to already have a perfect form which she won't pass on, or for Sasuke to go looking for that other place. At this stage it's not 100% certain that the third place is related to the slugs.
Yes, and remember Kakashi said Sakura was better than Sasuke and Naruto at chakra control. Back then at least...I think it will play a role in the future as well.