I quit playing around six months ago shortly after the second expansion was released.
You can now go up to level 80, there are stupid numbers of instances to do as well. As for bags, you can buy up to 28 slot bags but they do cost a bit.
You will find apart from the epic mounts that you knew there are also regular flying mounts, epic flying mounts, snow flying skill (this costs 10K gold) and 25K epic snow mounts (these are usually mammoths) which can only be used in the new frozen continent. Judging by the time you've been out you only know what used to be the old world, added to this is Outlands (first expansion) and the new continent which I forget what is called.
Making 1000g is easy, but these days it isn't much. Mining is still the most profitable profession out there since Jewelcrafting also uses ores.
There are two new races, Blood Elves and Dranei. The third expansion will bring on two more. The first "Hero" class, the Death Knights are almost impossible to kill on BG's and have practically outclassed Warriors out of tanking, so if you're looking at raiding or PVP then DK's are the way to go. These things out-aggro and out-dps warlocks and hold aggro better than most tanks (unless they are geared to their teeth).
It has become easier to acquire epic gear, but of course, there is epic gear and there is epic gear. The best stuff still drops at raids which are still on average four hours long.
In conclusion, I would advise you not to re-start WOW unless you are prepared to invest obsene amounts of time trying to catch up and unless you spend an average of 23 ½ hours a day playing you will NOT control the server economy. There are players out there with well over 500K gold. The servers belong to them.