I really doubt she gets nerfed.
I was originally attracted to the champion, seemed pretty strong and viable. After purchasing, playing as, and watching others play as Ahri I've came to the conclusion that she isn't worth it.
She's fun to play, but for the price of 6300 IP or X RP I can safely say it's not worth the purchase.
Her passive is alright, it takes a while to build up to proc though.
Her Q is fairly decent. The true damage is nice. It's easily dodged though, especially the return true damage.
Her W is fairly useless. You can turn it on for the extra damage but it's not much and it's not helpful in lane as you will mainly hit minions with it.
Her E is a CC skill shot that brings the target hit towards you for 2 seconds. You can hit minions with it which makes it hard to use in lane. It's nice and sets up your Q nicely but it's hard to land on the target you want most of the time.
He ultimate is nice, it needs a shorter CD though. It's 3 smart casting dashes in the direction you choose and it does damage each time.
If anything they'll be buffing her next patch. Her AP ratios are low, if they don't mess with them I expect them to lower the CD's on the ultimate and maybe change the amount of buildup for her passive to proc.