I don't have the 24-120mm f/4 but have seen some fantastic images here taken by Nikonite members. BackdoorHippie (Jake) mentioned in the past that it is a little soft, but he prefers the extended length over a 24-70mm lens. And he's mentioned the f/4 Holy Trinity which includes this lens, the 16-35mm f/4, and the 70-200mm f/4. So keep that in mind if you might want to eventually add the other lenses if you decide to go with the 24-120mm.
The other thing...I don't know which 85mm lens you own, but if the front filter is smaller than 77mm, you can get a step up ring which will allow you to use simply get all 77mm filters to use with all your lenses. For example, if your front filter is 67mm, then you'd get a 67-77mm step up ring. You DON'T want a step down ring. That wouldn't fit--those are used when a filter is smaller than the front threads on a lens--and you wind up with vignetting. Recently I purchased a Sensei 77-82mm step up ring through B&H. It's an excellent quality, and surprisingly the price for that brand isn't expensive at all.