So, here are my questions:I'd definitely get the 5D Mark III (keep the 5D2 as backup), the 24-70 II and the 70-200 II. That pretty much uses up all the bonus, but you now have both a top-notch body and glass. Besides, can always sell off a few items you already have to get one or two others.
1. Should I spend half my funds on the upgrade to the Mark III? The images from the Mark II are lovely, and focusing speed or extreme low light hasn’t been my issue. I do find my images at 1600 ISO seem fairly noisy, but I don’t know whether the Mark III would be substantively better, often enough.
2. What’s the best mix of overlapping zooms? The 75-300 that my wife and I have been sharing is convenient, so in some ways just replacing that with L glass seems like a good choice – in others, I wonder about a 70-200 and 100-400 combo. Or maybe a 70-200 and a 1.4x converter...)
3. How much use will the Tilt/Shift get, really? (I know, that’s hard to quantify an answer)
4. If I keep the 100 Macro, which I love, will I really need the 180 macro?
Thanks for reading what got much longer than I intended, and for advice and comments!
I think the 24 Tilt-Shift is a fantastic lens, but unless you plan to do architecture and interior photography you'll almost never use it's functions. I'm told the new 24-70 is just as sharp as the latest 24 TS, which is saying a great deal. Of course, if you need the shifts and tilts a lot (otherwise, you are probably better off renting for the few times you'd use it), this is what I'd get next, or perhaps get the 17 TS and sell your 17-40.
There's no question I would get rid of the 28-135, as well as the 200, since your 70-200 would make the latter redundant. Perhaps, the 35 should go as well, unless you want to use this in place of the 24-70 as a walkaround lens. Put the money towards 1.4 and 2x converters for the 70-200, or a tilt shift if that's your preference.
I'd talk you out of the 100-400. It's not that bad a lens, but it's been outclassed by more recent arrivals, especially with regard to autofocus and stabilization. And, at f:5.6, it's slow for so many situations. You're just as well off with the latest 2x converter on the 70-200, and if you don't need the full 400mm, get the 1.4x and you come out a step and stop ahead. I'd get both if it was in the budget.