sand *has* gotten a lot more common in the past few weeks. i blame jak3 and superc. i think rhyperior will be hard to fit on a sand team without creating too many weakenesses to grass, water, and fighting attackers -- they are already hard-pressed to find answers to those while running a mostly useless hippopotas (he has a few niches that he excels at, but countering azumarill is not one of them).
And it'll probably get even more common once Roserade gets the banhammer next month. I really didn't wanna see her go, I use her on a good number of my teams. Might as well abuse her while she's here for September though. (:
As for the "Milotic will be broken if Roserade goes to OU," I think many people forget that other Grass-types exist. Sceptile, Venusaur, and Leafeon can all still keep it in check, as can Chansey, Lanturn, Regice, etc..The only problem will be that it'd be slightly more annoying to kill now.
Rhyperior seems interesting, but I honestly don't see it becoming too big a threat, it's just way too slow. The Choice Bander would probably be the most deadly set, Rock Polish isn't that useful with all the Aqua Jet Azumarills and Vacuum Waves flying around.
I can't wait for Zam though, it'll be beautiful. So many options... Sub Encore, Sub Calm Mind, TrickSpecs, TricksCarf, Dual Screen, etc...I don't see it being broken, but top-tier for sure. It just sucks that it'll probably take over most Espeons spot on teams.
The only set I can see being a little overpowering is a simple Substitute attacker with 3 moves, which only Chansey can probably reliably take on because of his rediculous Special Attack stat. When behind a sub he can smply fire Focus Blasts at Registeel, switch, and KO him the next time he switches in. It also eases prediction and prevents him from being pursuit bait.