I have the 70-200 f/4 NON IS. It is great in most circumstances. In low light, it requires higher ISO settings than I would like. I am planning on getting the 135 f2 in Nov. The 2.8 version is just too expensive for me. $1000 is pushing it. I'm starting to enjoy prime shooting along with the savings.
You should definitely rent/borrow a 6D. I saw a significant improvement in image quality at higher ISO from the 7D. I don't even think about using NR until I get to 3200 (shooting RAW of course). Throw a nice prime on it. I'm dying to try the 135 f2 next month.
I'm glad they released this. It increases competition and might get Canon to release some new models they've probably been sitting on. Of course, I have no intention of every buying a Sony, but I like that they are good, which forces Canon to be good. I'm sure when Canon finally releases their large MP camera, I won't be able to afford it anyway, so it doesn't really concern me, unless it trickles down to the lower end models. Good for Sony.
Get the 5d3 now. You will get to enjoy it and it will probably sell nicely when the 5d4 comes out. It is definitely the camera I would have chosen if I were into video (and had 3 months of overtime). I sold my first DSLR (7D) after about 9 months for $500 less than I paid new. Not too bad considering what a rental costs.
A big problem I have is that I spend too much time on YouTube and forums. Nothing wrong with them, I just need to get out more. I am planning on going to 5 or 6 events next year, but more local stuff would be affordable. Attending Dragon Con is gonna feel like getting punched in the kidney
G.A.S. can be bad if you are poor. I don't mind wealthy amateurs buying lots of gear they don't need. Someone needs to fund R&D. It doesn't make them bad photographers. Bad photos make them bad. I'm in the semi-poor camp. I like to drool over the 1DX but it'll never happen :p. Getting some sweet overtime saving for the 135L. Doh! Feel some gas coming on
The 6D is great in low light. I only have issues when shooting action sports. Up to 6400 is great, 12800 is ok with some NR. If I could afford it, I would have purchased the 5D3. The 6D center point is like a tractor beam and works fantastic in darkness, but all the others are useless in low light IMO. It is not a problem unless zoomed in for a tight portrait where composition can be an issue. The 6D is better than the 5D2 in most aspects, but the 5D3 is better still.
I use an iPhone 5 sometimes. Mostly, I use the iPad mini. It's so much nicer using a tablet with the screen real estate. Consider a tablet. I'm sure they are cheaper than apple's lineup. First set up wasn't as smooth as I would have liked, but once there, it's easy to connect. I'm not sure how well the android version works. Once the device is connected, image viewing.and downloading jpegs is fast. There is a slight lag in the live view mode.