At the moment I don't need one, but in say 4-5 months I probably might need a second body if I'm in the wedding scenario and taking things more seriously and I'm also a bit of a hoarder when it comes to gear and gadgets. I suppose I may be more inclined to take the 60D with me to risky places as well, which I wouldn't do with my best camera, decisions decisions!
I've not used the kit lens a lot because it's not fast enough when combined with the noise levels on the 60D, it's practically unusable for low light. I must say though I was happy with it when I used it in other situations with half decent light, the IS was good, it was sharp and I didn't miss as much as I do with the 50mm. To be fair the kit lens I have is miles better optically than the original 18-55mm though, but obviously it's not going to work on my 6D. I think the Tamron 24-70 2.8 combined with the 6D's low noise capability covers the full range, and it's probably sharp enough comapared to my 50mm (which seems to miss focus/ be soft a lot at f/1.8). I should probably be stepping the 50mm down anyway and with the 6D and it's better noise capabilities I'm expecting equal or better results with a 24-70 2.8 over a wider range, is this a reasonable expectation?
I can't see me needing to go wider than 24mm, but would be nice to have a play with something like the Samyang. I've thought about the 85mm 1.8 but as I've got the 70-200 IS II would it be much of an improvement?
I think you're right about waiting to assess the situation though, that's definitely what I'll do. If I had to choose now I would keep the 60D and try them both out for a month or two, then buy the Tameron 24-70. I can't see the 24-105 f/4 being fast enough for what I shoot and for the slight drop in range I'd rather take the Tameron with the 2.8 for the same price. I'll upgrade the nifty fifty at some point and think a 30mm Sigma f/1.4 would work better for me than a Canon 17-40L f/4.
Thanks for the input it's much appreciated