Blizz stated in a watercooler that they're using the 1.12 database as a starting point. I don't think it's a stretch for people to assume that most game features and mechanics will be in their 1.12 state. The kind of stuff I would expect to see reverted would be numerous AV changes, but I seriously doubt class mechanics are going to be reverted. I'd be surprised if the threat changes that ruin pre-naxx encounters are reverted.
At BlizzCon, Blizzard announced that Warcraft Classic — the vanilla experience based on the game before any of its expansions — will go live next summer and be included in the standard WoW subscription. Interestingly, the entire sweep of game content will not be available when the game goes live. Instead, players will have access to Molten Core and Onyxia, the two 40-man raids that Blizzard implemented first in the original 2004 title. The company isn’t strictly duplicating the original rollout timeline; Dire Maul, Lord Kazzak, and Azuregos will all be available to kill as well.
":" - Any time a step ends in a ":" instead of a "." means that the next step is part of the current step you are on. This generally means the next step should be done while working on the current step. This means every "start working on" or "continue working on" will end in a ":". But this is used with other occasions as well, so keep this in mind.
Who is Joana? Joana, (AKA Mancow, or FuriousPaul) speedran 1-60 vanilla WoW from 2005 - 2007. I have been server first to level 60 seven times in a row, along with winning Blizzard's "First to level 50" contest they held back in 2006. I also have the fastest time through original vanilla 1-60 WoW in 4 days 20 hours. I have produced a very useful 1-60 horde speed leveling guide along with a 1-60 speedrun video.