You have excellent lenses, who don't really need upgrade, I would keep my money here. The improved sharpness of the 24-70mm II will cost you 2000$ and won't bring you "better" or "different" pictures; show them around, no one will see the difference. The only lens I would replace is the 50 f1.8, for the better ergonomics and USM of the 1.4, but if you're happy with the 1.8, just keep it.
I would as other said, buy a lens that allow you something different : close focusing (100mm macro, 90mm TS-E + macro tubes), perspective correction (24 TS-E II / 17 TS-E), wide aperture (24 / 35 f1.4, 85 f1.2 / 1.8 ), very long focal (400 f5.6), or even the 8-15 fisheye, all depending on what are you favourite subjects. As an alternative, a converter 1.4 vIII, would add a bit of reach to your excellent 70-200mm for relatively cheap.