I think, power up in this manga usually happen when characters get a fight. thus I belive sakura will get a power up when she get a fight in the next arc. and sage mode is one of them.
and I think goal or resolution make characters have a role in manga/story and if it resolve, than his/her story would finish. ex: rock lee, rock lee goal is to become a ninja even though he can't use ninjutsu, then it test with his cripple state and solve when his operation success. thus why in part two he doesn't get more focus since his story already over.
then again it just my opinion and prediction, I could be wrong after all.
I don't think Sakura will get another power up, she just got the Yin Seal not so long ago, and since we're near the end, there are ver little chances she could get another. I believe it's possible for her to get a fight before the end of the manga, maybe even before the end of the War Arc, but it's unlikely for her to get a power up. There was a time, I believed she could gain Sage Mode, but the Yin Seal was for me, the last PU. So, what I mean is that, if she get for example Sage Mode, it would be too soon, regarding her last PU, the Yin Seal. Just look, how long have we waited for her to get a PU, or even a fight.... Since Sasori? Hundreds and hundreds of chapter for her to only get a fight, and when she got one iin 632, it wasn't evena real fight against an specifical opponent, she was showing her strength against littles Juubis (even if I found that scene so badass!)
So, yeah to me, it's very unlikely for Sakura to get another PU before the end of the manga. But it's just my opinion, and who knows maybe I will be pleasantly surprised?