My thaughts on this are having you buy the battle chest, 2 month game card and then link that account to your vet account.

With 3 hours a day, if you are diligent enough, you will have a little over 3 days played time by the day Woltk is released. I know people that used this guide pre tbc and leveled pretty quick with it. http://www.wow-pro.com/node/754

You should be able to get close to 70 in this time but not sure if exactly at 70 (mind you if you get to 70 the day of release you will be fighting all kinds of people for kills on mobs and pick ups, so you may find that you would be fine leveling a week or two after people have started, with that you will be a little behind those that have a huge concentration on one area persay)