merv, I suppose it depends how much you use the 200-400 & what your main subject is.
I had a 300 F2.8 + 1.7TC & D7000 mainly for `birding`, but found it a bit heavy to carry around all day, but also wanted something with a bit more flexibility, kids in the park, bit of scenery, buildings etc. I find the new 80-400 ideal for 80% of my use & it aint too heavy to carry around all day. I previously had the old 80-400 up to a couple of years ago. I liked the range, but it was a bit too slow for birds. (this new one is faster & sharper)
If I was solely into wildlife/birds (or could actually afford another big lens as well) I'd love a 600mm or even the 200-400mm, but as an outdoor allrounder, the new 80-400mm is great for me. Using it on the D800E gives plenty of `cropability`.
I did lose nearly £1k on my 300mm prime, but it wasn't a purely financial decision for me.
I guess only you can decide, but if it aint being used (& not likely to be in the future) you possibly wouldn't miss it too much, especially if you can get a good price for it.
Let us know how you go on.