If it comes in at about the same price as the Nikon, I won't be disappointed. That's much less than earlier predictions.
I'll hang on to my current 100-400 until the price settles in, compare the quality of the two and then decide if it's worthwhile or not. If the quality is similar to the 70-300 L it will be worth trading up. I actually feel like, for once, I'm in a good position. Glad I picked up the 100-400 when Canon had it in their refurbished store.