In the PA podcast they mentioned the level 7 and 9 Slayer ones: Riposte costs 2 (or was it 3?) dice, and lets you make an immediate attack against an enemy who misses you in melee; and Whirlwind attacks multiple enemies, although they weren't clear on the specific mechanics of that. They also mentioned Riposte as a swashbuckler power in that L&L article way back, so I'm assuming that like Jab it's cross-listed with Duelist.
Aside from both sounding cool, this tells us that there WILL be higher-level powers that require multiple dice, which opens up the possibilities a lot.
I would expect to see:
More riders & status effects: Disarm, Stun, etc.
More movement enhancements
Accuracy buffs? (Bounded accuracy makes this tougher)
More protective stuff: e.g. Cover (+x to adjacent ally's AC when they take a hit)
I would not expect to see:
Overtly impossible/magical effects (flying, super jumps, teleportation, etc)
Non-combat bonuses (too powerful since they're at-will)