Well... sort of. I couldn't see any threads at the moment discussing this, but the fact remains that you are actually able to preload the Cataclysm data or atleast a great part of it now by doing a small tweak to your files:
1. Go to your Wow folder
2. Open the "wtf" folder.
3. With notepad (or mac eqiuvalent), open the file launcher.wtf
4. Find the part in that file where it says "accountType" and change it suffix from "LK" to "CT"
5. Repeat step 3 with config.wtf
6. Repeat step 4 with config.wtf
7. Launch the game via the launcher, hang on a for a few secs and behold as it starts downloading the Cataclysm data files, 700mb. (the ones that you pay more for to download as digi files than you do for the hard copy version... ie. save some money)
GL HF