The 70-200mm f/2.8L IS II USM is awesome for weddings and portrait sessions, very versatile and sharp. You already have the 50mm f/1.2L for low light and soft bokeh. Down the road, I'd sell the 24-105mm and Tamron and pick up the new Canon 24-70mm II or the new Tamron 24-70mm with IS. Or, pick up the 135L later on if there are times you want to go lighter.
1Dx, 5D Mark III, 5Dc, 40D, G1X, 15mm f/2.8 fisheye, 16-35mm f/2.8L II, 24-70mm f/2.8L II, Sigma 35mm f/1.4 DG HSM, 50mm f/1.2L, 70-200mm f/2.8L IS II, Sigma 85mm f/1.4 EX DG, 100mm f/2.8L IS, 135mm f/2.0L, 200mm f/2.0L IS, 1.4x III, 2x III, 600EX RT (3), Einstein