I have been around JD equipment all of my life and can say they are definately not the market leader in increasing the size of equipment. They tend to wait either for the market to weaken on the size of equipment they sell, or for others to develop and R&D the larger equipment market first.
Some examples would be:
Rode the straw walker combine market as long as possible,
Still don't have an air cart large enough to count,
Slow in getting 4WD tractors in the high hp range,
etc.
However, once they get into a market, JD seems to do very well. Some examples would be:
STS combines now account for major % of N American sales,
SP sprayers went from nothing to market leader,
Greenstar has become the "standard" that others now compare to.
So, back on track, I would think that it is still a couple of years till Deere has a good class 9 combine, and then everyone else will have a class 10 out. However, when Deere does release a class 9, the market will be developed enough, that Deeres sales of class 9 units should be good.