I wonder if they will discontinue the 24-105L. It seems they are replacing it with the 24-70/4 IS in the kits, which I expected. Does that mean they will phase out the 24-105L? If so, that would affect the value of the copies out there on the used market, though probably not greatly as the market got flooded. Also, it's possible they will replace it with a mkII version, upgrade the optics & IS, which would keep the used value of the current model flat.
Over all, it's a great walk-around lens, as others have said. I still use mine for weddings, though I've taken to using my 24-70L also, which I'd like to upgrade to the mkII but have rediscovered my version as being quite good on the 5DmkIII, after having used it exclusively on a 1DmkIII for many years it's become a 'born again' lens on the better camera. I missed the $1,695 sale on the mkII and maybe I'll catch it when it comes around again, but for now I'm happy with the original version on my 5D3 and the 24-105L on my 6D. It gives me one camera with great flexibility for focus, and another that is light weight and versatile with the longer reach and IS. I agree with the others, for $500, you might as well keep that lens.