The only thing, really, I can think of that would tempt me into upgrading at this point would be a significant increase in dynamic range; on the order of... Say, three-stops. Yes, I know that probably borders on miraculous but you asked. An increase of two-stops would give me cold sweats, and in all honesty would probably be enough to trigger an upgrade. Three-stops and I'd consider selling a kidney to finance things. Of course this all assumes Nikon does nothing to shoot itself in the foot which, really, is not a solid bet. Not even a remotely.