Kishi when he give powerups or events , he does not pull it out of his ass , he makes use of something already existing or something that has already happened
Examples
1)Koto Akatsumi on Itachi to halt edo tensei on him , the fact was planted when he gave Naruto the Crow long before
2)Naruto getting Kyubbi mode
3)Naruto getting Bijuu mode
4)Naruto getting Sage and Bijuu mode fusion , he delibrately drew it that way against his fight with Pain
Likewise , with Naruto and Sasuke , It was always hinted that they were opposing pairs , like Harashima and Madara , and he even brought out the fact that there was the two Sage sons that were opposing pairs , way before the Pain arc , when Naruto got the Sage powers , it was not totally asspull
Sakura getting a powerup would be totally asspull and even if she did , i doubt she will get powers rivaling Naruto's and Sasukes
Even though team 7 were shown to be successors for the Sannin , the Sannin were not exactly shown equal in strength either,