I kind of view WoW as having eras, in a fashion - although the demarcation of where a given era begins and ends can be a little fuzzy depending on context. Insofar as "Classic" is concerned, I think WotLK is the end of the Classic era of WoW, which is constituted by the original game (what was often referred to as Vanilla WoW), TBC, and then WotLK closing out. In that light, I think a Cata Classic is somewhat unnecessary at this point - although I wouldn't begrudge it a re-release either, I'd simply opt not to bother with it overly.