Well, I haven't run out of polyphony for years. I guess I don't utilize it to its full extent.
I remember thinking it was a big deal when they went from 8 note to 16 note polyphony on arrangers though!
People have been talking about a new Casio arranger for years. They seem content catering to the entry-level buyers, and they do have great-sounding pianos in them.
The talk on the Korg forums is that the next generation will have all the technology from their leading synth, plus the arranger features.
I don't think there is anything unethical about Yamaha's marketing policy. It's all about profit though, and I am just not going to play the game of paying huge amounts for relatively small upgrades.
As far as a big lead in totl arrangers, if there is one, Korg has it now. Yamaha has their sights almost totally on the home user, with everything to make him sound like a full band, orchestra, choir . . .
There are no wrong choices any more, just play what pleases you, they all sound great.