My feeling is that right now people at Yamaha are concentrated on the Tyros for obvious reasons; as soon as this frenzy is over, they will start to work on the 9000 too, in terms of support, etc.
Another feeling is that at least for the next generation of arrangers, Yamaha will not release another kb with all the features of the pro (sampler, expansion slots, 76 notes kb). This could be a good reason to buy one second hand, if you can find it.