If you need the improved AF and improved ISO performance, the 5DIII will be an upgrade. If not, you can live happily with the 5DII. The 24-70 you have is a great lens, but version II is even better. I have my doubts it will be a game changer for you though. So, in your case, I would either buy the 5DIII or save my money for later.
1DXII, 5DIV, 5DSR, 8-15/4L, 11-24/4L, 16-35/2.8L III, 24-70/28L II, 70-200/2.8L IS II, 100-400/4.5-5.6L IS II, 200-400/4L IS 1.4x, 17/3.5L TS-E, 24/4L TS-E, 35/1.4L II, 100/2.8L IS Macro, 300/2.8L IS II, 600/4L IS II, Zeiss: 15/2.8, 35/1.4, 55/1.4 Otus, 85/1.4 Otus, Profoto B1