This is why I have to rework my dream team, so it can survive Sandstorm teams, which are more common than any other other weather effects out there due to Tyranitar being the most used Pokemon in the series.
Also @Joshawott; I was using Garchomp as an example of the only Pokemon I see being given a berry by unofficial tournaments like Smogon because berries are rarely used by them as opposed to the VGC, which led me to believe that Smogon is the true way of how the game is played.
This probably means that legendaries will be useable in VGC 2013, as was also done before in 2010 (albeit not for the event-exclusive legendaries). The only question is whether or not the Unova Pokédex restriction will be applied; it would be a step back from the diversity of this year's eligible Pokémon. Either way, using a B2W2 cartridge will probably be mandatory for arbitrary (promotional) reasons.
Actually, one of the more popular team archetypes in this year's VGC 2012 format has been Tyranitar / Garchomp / Zapdos / Hitmontop / Metagross / Cresselia (or some slight variations of thereof). Notice how only two Pokemon technically abuse Sandstorm, while the rest is just a "supporting cast".
I raised a Scizor today just for that psychedelic duck xD
I wouldn't have called that a weather team in itself; with Tyranitar's Sand Stream mainly being there to disrupt any possible rain teams, as opposed to setting up its own strategy. One thing I noticed a lot in more recent battles is people replacing Garchomp with Latios anyway.