WiiFit doing good but it's not the announced fourth Age that some predicted and the longer Nintendo takes to fix their supply issue the more likely some casual buyers will loose interest in buying it...
That and it's going to be a while before there is a sufficent installed base of the board to support other products....
PS : WiiFit was in stocked today ( a thursday) at my Best Buy. Not sure if they held onto their allocation until MGS4 release or what....