I was thinking about this as well!!Good question... she's said to be a genius with genjutsu but never used any except by one dispel technique once in the whole manga. Considering that, she can't be a genjutsu specialist anymore, but she can still learn some quite good genjutsu techniques on the future. But the summoning jutsu is a must if she want to follow tsunade's footsteps like naruto and sasuke followed jiraya and oro.
1. Kakashi said that Sakura was originally a genjutsu user when she was in the academy...
2. What has changed in Sakura since then? .... Her Double Personality.
3. When Sakura fought Ino, it was her "inner-self" (so dubbed by the translators) that allowed her to break free from Ino's mind transfer technique.
4. Sakura no longer has that inner self, because Tsunade brought it to the surface.
5. I wouldn't be surprised if Kishi brought this inner-self back.... say for instance... If Madara has the ability to control people's actions (like if Itachi wasn't in control of his body when he killed the Uchiha)....
6. and then Madara forced Sakura to try and kill Naruto by using a Genjutsu... but Sakura's inner-self (who loves Naruto) will overpower Madara's genjutsu... THUS making her a powerful genjutsu user...