I would probably be happy with about 30 good voices, as long as they are MY voices.
That is the problem the keyboard mfgs. have. What voice to include that makes the most musicians happy. I never use accordion, harmonica and bagpipe (as metioned earlier).
In the Tyros II threat "The Pro" talked about modular keybeds. Why not have modular: keybeds, voices, internal amplifier/speakers, styles, harmonizer, etc.
Musicians can then have the arranger that they want.
Starkeeper