I'm actually not switching, but for fighters in D&DN, they do have something in common with encounter powers. Specifically Combat Superiority dice, which works a bit like fighter stances.
The (standard) action to regain a die sounds a lot like Book of Nine Swords, but worse. (In Bo9S you could regain a power by making a basic attack.)
Alas, not rogues, not in the latest version of the document. Then again, the 4e thief in my Greyhawk campaign is both powerful and boring. Move action: use stance to move and get combat advantage. Standard action: Gank. The rogue in my WotW campaign (4e converted) doesn't like thieves because they don't have to work to get combat advantage. (He's playing an eladrin rogue, so he can at least fey step flank once per encounter. Or fey step out of
being flanked.)
I ran into one of the players in my group-on-hiatus the other day and talked briefly with him about the Next campaign we're starting up in a few weeks. He was the player who attained the greatest rules mastery with 4E; he played a rogue, the only character to survive the entire three-year campaign from 1st to 17th level, and really got the whole combat advantage thing, and was always figuring out ways to optimize his capacity as a striker. Anyhow, while he's open and curious about Next, especially when I emphasized the "theater of mind" focus, I've had a tingling worry that he, and maybe one other player who attained similar rules mastery, will miss the AEDU paradigm.
The player probably won't like the D&DN rogue. If they only play rogues, there's a real problem there. There's a little too much "mother may I have combat advantage?" going on with D&DN rogues IMO. Bt they may enjoy the fighter, especially if they would have been a fan of the slayer.
I'm not sure it will be that different from the DM's side of the table and monsters will still effectively have the same "powers."
I haven't found most D&DN monsters to be nearly as tactically interesting as their 4e counterparts actually. Often there will be one interesting leader and several more boring monsters. I liked the giant black dragon though; the math is borked, but it did have thematically and mechanically interesting abilities, especially all the off-turn actions.
Of course PCs will still be able to do all kinds of things - everything and more that they did in 4E - but there won't be the same pre-made avenues of expression, i.e. powers. Except for spellcasters, of course.
What sort of things? I don't think I've seen anything like Handspring Assault in D&DN (that's a rogue power that lets you attack and then shift as one action, plus it's reliable so if you miss you can use it again). Or Deep Cut (inflict ongoing damage), or...
So I ask you, for those switching to 5E from 4E, are you worried about missing powers? For those having played the playtest, did there feel like a lack?
I only did a little playtesting, and played a wizard. Back then, there wasn't anything like encounter powers, but at least I couldn't run out of at-will magic

I didn't feel much of a lack as a wizard. We did have a halfling rogue, but this was the first packet, so they looked very different. (Back then, they were pure lurkers. Hide one round, gank the next. Frankly a lot more fun on the DM's side of the screen than the player's.)