Looking through the massive comment list on MMOChampion a lot of people are up in arms over this, but its all based on rumour and also on datamining of the PTR.
Blizzard know that people data mine it, and they have in the past embedded in some jokes like achievements that are just plain silly, but despite that I think some of this information is real. Some made me laugh, pretty sure that the class limitation changes will not go ahead, they'd really be unpopular with the hardcore that are left there and tear apart what's left of the original storyline.
In some ways though I like the idea of making the older zones relevant with the phasing, although in WoW's case if they carry on the WotLK approach it'll all be easy mode, and I severely doubt the 5 level cap increase, if they implemented that then no one would bother with new gear until part way through the raiding. A lot of it does feel like the typical fanboi wishlist of things mixed in with some facts.
Overall I'm surprised they have any hardcore audience left in the game, I know quite a few people who have left it over the previous expansion, perhaps I just didn't notice people drop out before, but the everything easy mode of the WotLK expansion turned a lot of people off. With the latest stunt of making all the easy dungeons drop the top level raid gear tokens it feels like desperation myself to keep people interested. If this expansion is a giant content reuse exercise then I expect that people will get bored of it very fast here since people were bored rigid of the content they reused for the WotLK expansion (the first and one of the two only raids available was actually a complete level 60 one, same graphics, same game play, I think this burnt out the hardcore that had seen it before).
This bit though made me laugh
Quote:phasing and daily quests. Most of the quests and mobs in the classic zones will also be redesigned to make leveling less painful. With the revamp, a greater narritive and sense progression will be offered to players. Some zones and dungeons will
Surely its a joke? right? :)
So if there are barely any new lands to explore I'd say there will be a lot leaving, if not at the start, but a few months in as people realise they've been running the same content endlessly before. Hence my vote is a lot of this is misinformation.