Heck, you probably have less than two months, really. Once the pre-release patch hits, we're going to be looking at whole new game systems to adjust to. New hit and expertise, hunters' needing expertise, no more spell penetration, new PvP power and resilience stats, new talents ... Women and men of Azeroth, the tide has turned. The Cataclysm is no more.
For people who've more or less done everything they wanted or needed to do and who were cooling their heels waiting for the new expansion, this is pretty much the unalloyed anticipation time. But for people who have things left -- bosses to kill, mounts to farm, that one piece of gear that just won't drop -- you now have an end point set out for you. After Sept. 25, you'll be leveling through Pandaria and the new dungeons, possibly PvPing in the new BGs, getting to 90 so you can run scenarios and get your own farm. You'll have things to do. Cataclysm will go the way of Wrath, The Burning Crusade and vanilla WoW -- stuff you may visit but that you're not likely to come back to very often.