Arceus-Grass should be going down in usage right now because of Ho-Oh and Lati@s, so that also helps.
Actually, I don't think it should be THAT effected at all. It's served me well on stall teams due to the fact it can double up as a check to Specs Kyogre and wall Garchomp a bit due to that WoW.
Magic Bounce mon and Excadril usage is definetly going to go up IMO, hazards are still as prevalent as they were earlier, and the ability to clear them from the field is priceless (especially for Ho-oh and Multiscale Lugia even though spinning and Magic Bounce is a bit shaky...). Kyurem-W and Black are actually a bit overated IMO, they aren't the fastest things in the tier and they both have 100% sure fire counters, Chansey for white, Arceus-Steel for Black (YES CB FUSION BOLT WILL NOT 2HKO (well it has a less then 1% chance to do so... this is assuming the 252 HP ev spread btw)), I think they'll die down in usage after the hype is gone. Sand IMO will rise. Tyranitar can check all the new threats (Latias, White Kyurem, Regen Ho-oh, etc.) except Black Kyurem, and Hippo has him there.