The plug looks the exact same and I mean the exact same. But the charger looks alot different to me, and not just because of that turquoise color on the nintendo one.
There's no way to tell if Nintendo's planning on a charger or not. Just because it uses AAs doesn't mean it can't be rechargeable. It's prefectly possible to buy rechargeable AA batteries And they're probably cheaper than a custom made battery pack. My wireless mouse, for example, uses rechargeable AAs. It sits in its dock and recharges them. And with the USB port on the bottom of the controler, it's perfectly possibly for that to be used to plug it in.
So really, it's just up to Nintendo and wether or not they put the needed hardware in the remote to make it rechargeable.
Today IGN clarified a little more. They said that AA's were planned, but that doesn't rule out a battery pack. I should have thought of this before, I used to have a camera that took AA's, but if you managed to get ahold of the dock for it, there was also a rechargeable pack you could get.