Nerfs are basically off until a week or two after first preseason patch (next week.)
The changes to the turrets, minions, and all the other micro changes they're implementing are going to shift the meta, and individual champions strength and weaknesses. So don't expect balance patches any before December, so they have time to analyze where all the champions line up.
Trust me im on your side with most champs. Akali Graves Irelia Sion Jax Kayn etc, but the new meta may take them down a few pegs.
Because most of you are saying the same thing, I'll reply here as a general response.
I'm not saying the turret and minion changes are going to magically balance everything, but there is no denying that the meta will shift, and certain picks that are "op" right now are going to be less op when the changes occur. This is due to the longer laning phase, more durable turrets, and stronger minions. These changes will drastically change the top lane (specifically) and jungle early game. No longer will it be "Force the turret down at 8 minutes after one successful gank." If I had to guess, the metas going to shift to more gank-heavy junglers capable of repeatedly ganking a lane to farm tower plate gold. I also believe the metas going to shift back to farm-heavy top laners like Nasus, who now have a safer, longer laning phase.
The nerfs aren't coming right away because no one can predict how all these changes combined are going to affect the current meta. Once they have the data to analyze, they will have a massive balance patch (like every preseason) where they bring champs that are falling behind up to par, and tone down the champs that are still broken.
Its really easy, especially on the boards, to get into this constant mob mentality where you always have your pitch forks pointed at riot, but regardless of how much you complain about them, they still brought us this game that we play. If you're on this boards, theres no denying that league is a major part of your gaming repertoire. I'm not saying they make great decisions 100% of the time. (-3 ad to graves, -5 movement speed to irelia??) but they overall keep this game and its servers running. Pre season is a major shift, and them not just throwing balance patches out every time boards complains about something is probably the reason they've stayed strong for so long.