I've been playing RU for a bit, here's what I see going / staying / being great.
I see Shell Smash, or various Pokemon with the move, either being removed or being over-prepared for. They are so absurdly dangerous due to the low Speed and sometimes low power of the RU Pokemon. A Pokemon like Omastar often has a defensive demeanor, but now it's not safe to treat it like that, if you let it set up, you lose.
Cresselia is the most overrated Pokemon, as usual. I have honestly no clue why people think Cresselia is so good, and I didn't in Gen 4 UU either. It's so weak. You can switch anything into it and still beat it because you can use status or SE moves to 2HKO it. Sure you can't OHKO it but what does that matter when it can't 9HKO you? Especially with Honchkrow, Yanmega, and other incredibly powerful Pokemon able to destroy it.
I actually put my money where my mouth is; my team relies on this fact. Scarf Medicham sweeping is as good a strategy as I've seen so far. Speaking of...I have not seen Scarf Medicham besides on my team....why? I've seen Gallade, Primeape, and even a goddamn Eviolite Machoke.
Almost nothing can switch into a 480 Attack 130 Base Power Hi Jump Kick. The only things that can are easily removed by Pursuit.
That's all I have for now.