i'd sell it, and then maybe buy a cheaper sigma 17-50OS, and just use it exclusively on the 60D...you'd save some money, and not give up much/if any IQ wise...i mean if you're going to hold onto the 60D anyways, might as well have a lens that works best for it
if you go for a FF lens, you're either giving up f2.8, IS, the wide end, or the long end...
16-35mm f2.8, gives up the long end and IS
17-40mm f4 gives up f2.8, IS, long end
24-70mm f2.8 gives up IS, wide end
tamron 24-70VC only gives up the wide end
24-105L gives up f2.8, and the wide end
if you can't afford to keep a lens just for the 60D, then you'll have to just decide what your priorities are for use on the crop