Your starting level will be automatically determined by the attack/defense stats in your vault and character, which means you don't have to put on 34 gear before the Taken King releases. If you are clearly a veteran player, i.e. raid weapons, many upgraded exotics, a lot of 34 tier gear, you will start as level 34.

I have 3 34 characters done raids atleast 100 times so I will start at 34?

I'm so confused