These are my personal musings on what to expect / what I'm anticipating for Nationals at this moment. These could possibly change in the coming weeks as we get results in from other countries' Nationals, as that will have a major bearing on what US players will be running. This list is in no particualr order, and I'd rather not group the decks into tiers until we see some results.
Night March - Obviously a force to reckin with, following the ban of Lysandre's Trump Card. The deck is simple, fast and consistent. Seismitoad has long kept Night March in check, but with no way to ruin its setup, one turn of items can be all that Night March needs to start pushing 180 every turn, especially with Shaymin around. If you're not playing this deck yourself, you should definitely keep it in mind.
Seismitoad Variants - I would love to say that the big blue frog will no longer rain on your parade, but he isn't out of the game completely by a long shot. Players will need to be more conservative witb disruption cards, but VS Seeker still allows Team Flare Grunt and Xerosic to be recovered, and Shadow Triad can get back Hypnotoxic Lasers- a tactic that has been employed since even before Toad hit the scene. The Crobat Varient is the least impacted by the LTC ban, and is still capable of two-shotting most Pokemon-EX- the Item Lock will most often keep the opponent from powering up anything that can one-shot a Toad every turn. Additionally, Mewtwo-EX can be used to give an extra late-game punch once the opponent has burned through much of their deck and Item Lock is no longer necessary.
Colorless Mega Rayquaza Variants - This card has been hyped long before Roaring Skies hit the tournament scene. Seismitoad has and will cotibnue to be a limiting factor for Rayquaza, as well Enhanched Hammer, but being able to one-shot any card in the format (other than Waillord-EX) should not be overlooked. The Bronzong variant of this deck is particularly versatile.
Bronzong Variants - With so much Special Energy around, there is much fun to be had with Aegislash and Cobalion. LTC's ban means those DCE and Rainbow Energy are gone forever, so that Righteous Edge is a lot more dangerous. While Night March can take out an Aegislash, it does give the deck a good run for its money. While I don't see Metal as having any autowins (except Mega Gardevoir, but you won't be seeing that), it does have a lot of 50/50s and slightly favorables, and doesn't autolose to anything that's popular.
Mega Manectric Variants - Manectric comes across to many as a natural counter to Rayquaza. There is some truth to this, so long as Altaria can be dealt with. In addition both Assault Laser and Turbo Bolt are reliable attacks. The latter is especially good as it powers up your bench while doing steady damage. Personally, I feel like Manectric is too slow to keep up with Rayquaza's speed, but many players will flock to this deck regardless. Be prepared to have an answer.
Raichu Variants - Here's the beef. I think Raichu is a much more efficient counter to Ray,as it can be charged up with just a DCE and give up only one prize. With Sky Field and a Muscle Band, it will also deal the magic 180 to take out a variety of threats, and can go toe-to-toe with Night March when paired with other attackers. Like Seismitoad, Raichu players will need to be more conservative and have a backup plan, but there's really lots of options. Croboat, Fighting, and Dark versions of Raichu all seem play-worthy.
Primal Groudon / Wobuffet - Slow and steady wins the race. This deck has shown itself to be quite the force once it gets going. Groudon sits quietly on the bench until it's ready to go. Focus Sash makes it impossible to one-shot, even if you can hit that 240, and the inclusion of healing cards like Dragonite ROS make the Continent Pokemon a superpower indeed. However, the slowness of the deck makes it vulnerable to Night March and other speedsters, and if your Primal Groudon is KOed, you lose everything. The popularity of this guy will depend largely on Seismitoad's success in the coming weeks.
Aromatisse Variants - That promo Regirock isn't just a novelty. It provided a safe haven for your precious Rainbow Energy. "Fairybox" is a versatile deck when it gets going, and having Malamar-EX around can slow your opponent down significantly, with many decks relying on cheap or free retreat rather than switching cards. Mega Gardevoir could have a niche role, but I wouldn't expect to see it doing well due to so many things being able to one-shot it. Waifu's going to have to wait until the rotation hits.
Gengar and Donphan - I'm grouping these into a single category since the strategy is similar their role in the format is much the same. These two decks have the best Night March matchup in town right now, but fare poorly against most of the other big-name decks. If Night March is all that it's hyped up to be, you can expect these two to rise up and take it down.... but they're risky plays due to faring poorly against the likes of other decks.
Yveltal - Eh... I dunno. With Raichu and Manectric running amok, and Rayquaza and Night March able to one-shot it with ease, it's funny to mention this deck at all. But with its long success in spite of everything against it, I think it's worth listing this deck based on its track record alone. It's a good counter to "anti-Night March" decks like Gengar and Donphan... but that's provided the format goes full circle. I'm very much on the fence about Yveltal, but I'm not ready to ride it off as not viable at all.
Not Invited : Flareon, Dragon Rayquaza, VirGen, Fighting Variants (except for Groudon and Donphan), Mega Latios, Mega Gallade. These decks are either too flimsy or just have too many negative (or not enough positive) matchups to deserve a big slice of the pie. They may see some fringe play, but you shouldn't be worrying about countering them.
