You should not wait. By Cliff's own admission, the II was engineered with plenty of room for expansion. I take that to mean, the amps and effects can become more and more complex, as he learns and makes new personal discoveries, to add realism to the unit's performance and take more advantage of the headroom in the processors. MIMIC is one such epiphany.
The thing the AXE III could take advantage of would be the advances in computer processors and miniaturization of memory and parts, that have undoubtedly already occurred and will certain widen the gap between the II and the III by the time it's time to release an Axe III. I would've liked there to be 2 effects loops so I could to a pre and post amp insertion of other gear in the same preset. And I would have wished that the FX loop did not subtract from the CPU usage on the effects side. Other than that one really selfish wish, the Axe II is perfect.
But if you buy an Axe II now, and an Axe III comes out in 2 years, your Axe II will still be earth-shatteringly awesome. I think it will be at least 2 years before we see a next gen. I would feel worse for a guy that buys a II because that's the only thing available, and then see an announcement about the III a week later, and see the prices of the in-stock II's drastically reduced. Those are the losers here. But you, with possibly 2-3 more years of industry leading sonic and performance supremacy should not wait any longer.
PS - Guys, if Adam's dog gets a T-shirt, I frickin' want one too.