Some of the things we have to look forward to in Cataclysm are the addition of a reworked Eastern Kingdoms and Kalimdor so that flying mounts will finally work to get cheap wow gold.
Another is that Blizzard is going to be re-using some of the popular instances of the old days. For example, we just recently heard about Onyxia being re-used as part of an anniversary event with some 232 and 245 item level gear. As far as I know, Ragnaros will also be back in this expansion about wow gold.
We are also learning that no new continent is planned, which is a stark contrast to what players are used to expecting out of the expansions. The honest truth is that when a game company starts rehashing content as Blizzard plans to do (and they have already begun doing so) it is clear that either the creativity department is running out of ideas, or they are trying to pave the way for a new MMO to get cheap wow gold. Could they be trying to weaken World of Warcrafts influence by releasing less content so that the new MMO can outshine World of Warcraft about wow gold?
Further, it is looking like the cap of the next expansion will be 85, an increase of just 5 levels compared to the 10 typically seen from previous expansions. It is possible that they could really just be making the levels twice as time intensive to complete, but I think the real goal here is Blizzard has heard a lot of complaints about people trying to level alts that they want to make it easier for people to reroll and experience end game content.