Kaivax, a WoW forum community manager, revealed that WoW Classic's class design, battleground mechanics and stats on existing items will be set to their 1.12 state, despite the game releasing content that expands beyond that. This removes "progressive itemization," so if the stats on a specific piece of equipment was changed during the original updates, that won't take effect in this version.
What add-ons can do has changed over the years and have become much more sophisticated as authors have gained years of experience and savvy. We’re not 100% on a concrete solution to what this means for WoW Classic yet, but one thing we know is that we’re not going to roll all the way back to the 1.12 add-on API. Doing so would open the way for nearly complete automation of combat decision making allowing for “bot” behavior that is counter to the core WoW gameplay experience. This is one thing we know we don’t want. On the other end of the spectrum, the modern API offers some additional functionality for creating social features that could also undermine the authentic classic experience. We’re still figuring out the details and looking for a good middle ground. We’ll be keeping a close eye on feedback from the community and add-on authors on where we should be setting those boundaries.
Classic WoW is the highly anticipated, upcoming (re) release of the original, first World of Warcraft version, known as Classic and by it's other popular ice-cream like name: Vanilla WoW. Dubbed Retail Classic, or Official Classic by the playerbase - it was finally announced by Blizzard in November 2017, after a lot of pressure from the Private Server World of Warcraft community, since the latter's shutdown of the most popular Private Server called Nostalrius which featured the first WoW version in two separate PvP and PvE servers.