I hope not. The point of a wireless mouse is to be wireless. 50% in a day's heavy use? Get an Apple battery charger. Apple's rechargeable AAs are great and last me about a couple of weeks under heavy use.
I use mine literally 11-14 hours a day and they last 3-4 weeks no problem.
It would be a great feature to get an mouse theat can work on a glass surface and a backlit wireless keyboard as part of a redesign, everything else it's just perfect as it is now.
It's called a ball mouse. I guess in theory they could do it with an accelorometer, but I somehow doubt that would be accurate enough for people's expectations.
Somehow I doubt I'd get the same kind of battery life. My Logitech mouse has to be charged every 6-7 days without fail, and I'm using fresh Eneloops.
I think Apple will update the keyboard. I read rumours about it and suspect it might....though I won´t cry if it won´t, it´s all ready the best keyboard on the market.
Magic mouse I suspect will stay the same. It looks beautiful and it is newer than the keyboard design. THough, I really don´t care, I won´t buy it. I have one all ready, which is one too much...it collects dust, it´s a crap mouse. so I´ll choose the touchpad instead.
Companies such as Logitech have had "Darkfield" mice, which work on pretty much any surface, for years.