Wildlife with OM-D-M5 & new 75-300 - an alternative?

I want to go into wildlife photography. Wildlife photography needs long lenses. Furthermore it's not so wrong to have water sealed bodies and lenses. A good autofocus system should also be helpful. If that all together wouldn't weigh tons - really fun!
So, what do you think about the Olympus OM-D-E5 camera with the new revised Olympus M.Zuiko Digital ED 75-300mm 1:4.8-6.7 II lens for wildlife photography? This combo offers a '600mm' lens, at a weight of less than 1kg for about 1650 €. Okay, the maximum aperture at the long end being 6,5.
Thanks for Your help!
Fujidanny