It certainly would make sense to sell just one keyboard that was capable of accepting upgrades...be it hardware or software.

This reminds me of the IBM stance on computers way back in the beginning. IBM said the money was in building computers and hardware. Microsoft maintained that the money was in software.

Somewhere along the line some Company is going to market an arranger that is really upgradable, and only excepts that company's software and hardware .

When that happens, that company will be the new Microsoft of arrangers/keyboards.