This very topic has been crossing my mind the last few days. The more I think about the "popular" decks not winning the more I think they will win. Like here's some of my thoughts on my possible "popular"'s not winning.
Jumpluff-This is pretty popular right now, it's biggest ish is the HP. Like its a strong hitter and with an expert belt and shaymin tech it makes it better but that's not enough. Especially since a lot of decks in format right now can work around the active and snipe like crazy. Shaymin is an easy target and knockout and if you work up that Jumpluff with the belt and say knock out that Shaymin your opponent can take 3 prizes in a turn. That's pretty much game. Jumpluff is good, fast, and an all around o.k. deck but I really don't think it'll win states. But since its so popular I'm sure it'll win a few just from sheer abundance in the meta. I say if it really is as popular as I think and assume, it'll win around 2-5 states.
Gyrados-This is another one of those popular decks but with the crazy amount of Luxray GL's in play he can be an easy kill. And it's easy to quickly throw a belt on Lux and then get it off with a PokeTurn. It's a solid deck but I really don't think it deserves to be among a winning state deck. It will win a few but I really don't think all that many. It'll probably win around 5-7.
Donphan-This deck is bad. It's really not that great. It's super easy to work around and I mean with the SP's dominating, it's hard to keep that "OH80FOR1+BELTLOLOLOL" on an SP. Now to be fair 80 can knock out any basic SP but like, if it was really all that great don't you think there'd be more Rampardos or Kingdra? People who are like "DONPHANisBESTguys" Probably don't realize that Kingdra is completely better in almost every aspect. (But I think that's more than less my opinion, mostly from exp). Plus x2 weakness! Completely open to those Jumpluff everyone likes. But it is rather popular mainly with Flygon, and Flygon is pretty superior to Garchomp. So a FlyPhan should trump LuxChomp, but I think that would be a very good game. (Especially since most LuxChomp's are running really odd tech's in them now). It will probably win a few though. I've yet to lose to it but I mean, popularity and, etc. will make it a winner in a few states. I think it should win around 5.
Shuppet/Dunsparce Donk Variants-This is a pretty run of the mill donk deck. It's really bad against the super popular Dialga and Gengar decks. Plus Looker's anyone?? It's a donk deck... it should NOT win a state by any means. If it happens to get by it will win no more than 3 states.
Typhlo Variants-Another deck that get's the x2 cripple award. It's a solid deck and it seem's like a lot of people are trying to get these to work. I don't think that it's super popular but it's worth the mention. It is really bad against Gengar and Power Locking decks though.
Gardylade-I really hope that this jumps back into popularity. It's always been a good deck but now with DCE it's gotten a little of a power boost. It's like I said though with Typhlo, I don't think it's super popular yet but you should see some. I don't think it'll win any states though. Set-up decks are just not ready to be in play again. Not yet at least. But it is a really good power locking deck but I really don't think it'll be as popular as last year.
Amphros-I've been hearing some buzz about this deck lately, sadly I think it's too much to set up and is too early to be a good deck. I felt like I should mention it though but sadly this will win zero states.
Stupid LEGEND Decks-Ok guys, really stop. These are bad and your not going to win anything with them. Stop trying to use that awful Lugia. And both are a pretty easy kill.
EDIT: Magnezone-I have hopes for this deck. I think it could work but since it's a newer deck to the popular kids table I don't think it'll be too popular or that much of a state winner. I think at regionals when we see all those funky decks, we could see some more of it.
So that's some of my thoughts. But just respect that, that just what I think. I also think that the winner's are really going to be more SP based. I think the ones that will win the most are; LuxChomp(+variants),BlazeChomp(+variants), DialgaChomp, SP Toolboxes, Palkia SP Lock, Gengar, Flygon with somekind of odd player in it, and probably really odd rouges. Who knows though. I've been trying to stay away from the Pokemon forums so I can just focus on making myself better and not getting overhype for states.
(Also good luck on all your matches in states!)