A couple of concerns regarding the current ideas for "legacy servers" Blizz may create.
First of all, they have the idea to give vanilla free with the retail WoW sub. I would like to point out, that if that is the only way to sub for vanilla, they will use each and every one of us as a statistic for the number of subscribers to current retail WoW and say that we support it.
Secondly, it has been mentioned that they may release a "legacy collectors edition" that may contain in game items or mounts/skins. This buying of in game items is completely against the concept of vanilla imo, and is a slippery slope to pet shops, WoW tokens etc.