I don't know . . . I'm punching in the air right now, the way I imagine the game working and I can't imagine needing a longer cable unless you really plan on flailing about. Who knows? I guess we'll see, as EA is working on the system and it seems like they would be crazy not to do this. In fact, I'll bet the Fight Night team is watering at the mouth to give it a go.
The following article gives some useful insights into how effective the Wii's controllers are likely to be for fighting games and interestingly actually mentions Fight Night:
http://www.xgaming.com/newsletter/Wii%20Dupe.shtml"While the IR tech can aim relatively well, it is not likely as accurate as a mouse. This means that FPS games will not likely be better played with the Wiimote than a mouse for accuracy, though being able to point and shoot at an enemy may still be better overall. And while the accelerometers can detect motion, it cannot tell exactly where the controller is in 3D space nor exactly how much you have moved it. This means you will not be able to control the next Fight Night on Wii by punching like a real boxer in real time. Alas, virtual realty has not arrived to this extent just yet."
Some other paragraphs from the same article that caught my eye:
"I am not saying that the Wii will not be awesome, I still believe that Nintendo will win this console war. But it seems clear to me that the Wiimote cannot 'detect its exact location and orientation in 3D space' with 'pixel-perfect accuracy' with the technology it was using at E3. Perhaps it still will. Gamers like me want to know what the Wii will and won't be able to do."
"The Wii hardware we exhibited at E3 2006 was made specifically for the E3 show and is not the final mass-production version. Some of this hardware was cased in Nintendo GameCube housing," - Nintendo
"Today we learned that the Wii at E3 was running in GameCube shells, perhaps the controller and the hardware are still being upgraded."