Arena Season 5 begins on December 16th. That gives everyone a little over a month to get their 70 character to 80. That should be enough time for most people to get to 80 if they only play one character to 80. For Death Knights it will be a little bit tougher...
There are 2 difference specs I would like to try at 80. One involves BM / Marks and the other is BM / Survival.
This is probably going to be very similar to most PvP BM Hunters come 80 (although I prefer Hawk Eye in all my builds). Here is the BM / Marks build:
The BM / Survival build is my personal gem that I really want to try out come 80. The premise is attaining Hunter vs Wild which gives you and your pet a lot of attack power, which BM lacks (in both the Hunter and pet). It also makes Stamina the best stat to stack by far. I chose Savage Strikes instead of 2 points instead of Improved Tracking because I find it really annoying to switch from Tracking Stealth since tracking is on the GCD. Here is the build: