Anyone that thinks Yamaha are going to build something like a KTM 9x0 ADV is going to be extremely disappointed. Just as they were when the current SuperTen came out.
That was always going to be a 1200GS clone. This is inevitably going to be an 800GS/800Tigger clone - decent tarmac road tourer, not open class desert racer. Even KTM have gone that way with the move from the 990 to the 1200.
I don't agree with GulGo about the end of the 660Z. It's the biggest selling of the three models, can't cost much more than the X or R to produce, but sells for a lot more. The 'adventure bike' market is growing, it's taken Yamaha a while to figure that out, but it's not surprising that now they've finally cottoned on they would try to fill all the sub-divisions of the class.
BMW canned their 650 class bikes, assuming everyone would want to buy one of the new 800 multi-cylinders. They backtracked fairly quickly on that mistake, and now have offerings in all three capacities.
IMO