The ones that are really getting a lot of note for the first couple of events are:
AMU - The premise is the pixies; Mesprit, Uxie, and Azelf. Its a speed deck that usually gets set up around Turn 2-3, though with a bad list can take a bit longer. It's able to deal with heavy stage 2 lines in relatively low time, but has issues with basic lockdown pokemon such as Mewtwo LX, Mightyena, and Mr. Mime. Debatably the best deck for the beginning of next season, but may end up slowing down upon IFIDS.
Kingdra - Vastly overrated deck, but still has a lot of potential to see powerful play at the beginning of the season. It has the ability to turn 1, but Turn 1's have not been as possible this season due to Roseanne's, Call Energy, and a lot of great starters with Call for Family options. HEAVILY reliable on Claydol to even be effective. With an efficient lockdown or quick damage, he can be stopped pretty abruptly. Initially debated as the best deck of next season, but the hypes died down somewhat.
Scorpio/AKA Gliscor Guerrila - A relatively quick deck revolving around Gliscor LX's hit and run attack. The premise is simple. Get Glis and use its attack to switch into a wall/staller like Mr. Mime or something of that sort. Kind of similar to Flariados in essence. IMHO, the best deck of next season, but still argued as inferior to AMU. Has problems with damage spread.
Magnevire - Extremely set-up oriented, but has every resemblance to a powerful blue deck late game due to paralysis control, energy manipulation, and heavy damage. Uses Magnezone Level X's Cyber Shock for free paralysis and large damage, and discard manipulators such as Electivire SW and Rotom MD to return the discarded energies to play, as well as the energy transfer from Magnezone Level X. Heavily reliant on powers, but not as bad with Cessation Crystal leaving format. Not as well known as the rest, but will probably be seen somewhere down the line, and may even become a better deck upon IFIDS's release.
Random Spread Variants - We'll be seeing a number of these thanks to Yanmega, Bronzong MD, Froslass and the works. Whether you think it or not, they'll still be seeing play.
T2 Beedrill/AKA Rock Band - I still don't see why it was called this, but whatever. Its a speed deck that still has great efficiency because it does not lose much from the format change. Azelf LA will help it out a lot, and Buck's Training will improve the draw that it has.
Torterrible - I think even after Nationals that this deck will see play in some areas that won't be seeing as much AMU due to its incredible amount of HP, devastating damage output, and ability to heal back that lost damage, in addition to controlling who comes out when behind in prizes. AMU annihilates it, but watch for it to be seen here and there.
Mewtwo LX Variants - To stop the AMU craze, Mewtwo will be seen here and there in order to keep it in check. How will it be played? Noone knows yet.