The E5 replacement has just been announced....

Sergey, I am a birder, and my main setup is E-5 + 50-200+ec1,4 & ec2,0.

If I want to see in the viewfinder EXACTLY what I see in my E-5 (100% coverage, not 125% or whatever), what setup would you recommend that has a 4x bigger sensor? I've tried the Sigma tele route on a D700, and please don't mention sigma tele zooms. They are not nowhere in the same class (the x-400 or the x-500mm lenses) as the 50-200, and they dont track as well as Nikon's own glass.

It might seem like a provocative question, but in reallity it is not. If there is no valid E-5 replacement within the next 18 months, I have to change systems. But to what?