Nintendo is stuck between a rock and a hard place here.
There is a solution for the lack of support but that solution comes at the price. A price of possibly 1 Billion dollars.
What Nintendo can do is stop production of the Wii remote and mandate MotionPlus to be integrated into every Wii Remote. The time it would take to replace manufacturing equipment and retail statistics would cost a whole lot of time and money. We can only blame ourselves. We are buying Wii remotes like crazy and if Nintendo would to halt production not only would they have a bunch of angry people, Nintendo would also lose tons and tons and tons of money.
But it would have its benefits and MotionPlus support would shoot through the roof. If every Wii Remote produced from February 2010 and on had MotionPlus integrated we would see plenty more games. The problem here is that Wii Remotes outnumber Wii Remotes with MotionPlus by like 100:1 ratio.
Although this move would upset consumers at first, it would then be accepted with a smile. Like how every year there's a new iPod. People hate it but sales shoot through the roof. So new Remote models(not add ons) would definitely be a good if costly move in the end.