The variants of the 70-200 are pretty much the go-to choices for the telephoto. I have the f/4 L IS and I'm pleased with it. That extra stop of the f/2.8 would be nice, of course - but it's expensive.
Rumors have it that the Sigma 70-200 f/2.8 is 95% as good as the Canon, for half the price. Probably worth considering, based on your lens budget.
If you really do a lot of macro, the 100mm Canon f/2.8 L Macro is generally the go-to choice. But now you're getting into lots of overlap in focal lengths, since all your lenses would cover the 100mm focal length. How much true macro shooting do you really do? Is it something you're seriously considering pursuing?
For lots of versatility, I'd probably go for a wide-angle instead of a macro. I recently got the Rokinon 14mm f/2.8 (full manual) and have been very pleased with it. It's a bit of work to use, but it's so sharp.
As far as flash, you've got a couple of ways to go - a single expensive flash (e.g. the Canon 600EX-RT), or several less expensive flashes. I went the latter, picking up the 430EXII, two Yongnuo YN-560s, some Cactus wireless triggers, and some accessories (stands, umbrellas, etc). The 600EX-RT is supposed to play real nice with the 5D3, using Canon's new radio-based wireless technology (as opposed to the optical wireless from all the previous stuff), but I haven't personally used it.
Opinion 1: A couple of cheap flashes off the camera will get you MUCH more interesting results than one expensive flash on the hotshoe.
Opinion 2: Get the 430EXII flash for $250, put the rest of the flash budget into your lens budget. Then in the future, as you start to develop your skills with the flash, invest a bit more into getting the flash off the camera: stands, triggers, slave flashes, etc.
One more thing: Get the PDF at the bottom of this page for information of the very complex autofocus system. The document is for the 1Dx, but the autofocus system is essentially the same.