I've had the thought lately of tinkering with my setup. I primarily shoot a lot of high school sports in poorly lit gyms, which is where the 85 (1.8),135 (2.0), and 200 (2.8) get lots of use. I use the 24-105 and 70-200 as "walk around lens" in outdoor settings for family trips, wildlife, etc. I could probably throw in about $500 in cash in any buying/selling I might do. Options I'm considering are:
Option 1: Sell the 200 prime and 70-200 zoom to fund a 70-200 (2.8) non IS. I find myself not using the 200 prime much in high school gyms, as the length is just too long most of the time. The freedom of the variable reach of the zoom in the 2.8 might make sense, as the reach of the 135 is not quite enough at times. The non IS doesn't seem to be a real issue for me as I'm usually shooting at least 1/400 or faster indoors most of the time.
Option 2: Sell the 70-200 zoom and kick in another $500 to pick up a 70-200 (4.0) IS. With this option I'd just live with the all prime set up for indoor sports shooting. The appeal of this option is I've found the IS on the 24-105 to be nice to have in general walk around shooting in low light. The fast primes I have can help with the low light in walk around shooting, but I like the convenience of the zoom.
Option 3: Save until I have $1,000, along with selling the 200 prime and 70-200 zoom, to fund a 70-200 (2.8) II. I'm sure I'd love this lens with all the great things I've read about it. The only real negative is it would be my long zoom for walk around purposes and its size might be cumbersome.
Right now, I'm leaning toward option 1, simply because it involves no additional cash, gives me a faster long zoom, and is still a reasonably sized lens for carrying around for everyday shooting. Thoughts . . .