According to Tigole, Blizzard will "try to patch" the Wrath of the Lich King beta today. Storm Peaks will open back up and should not crash the sever. No word yet if Naxx will be introduced in this patch. The servers should be up between 4:30 p.m. PDT and 6:30 p.m. PDT.
The XP required to level will also be reduced by 10% this beta patch. Things should go faster for all you playing around with leveling.
Finally, there will be a new beta realm opening up named Murmur. Tigole mentioned that the premade characters should not have been made available on the existing realms. He tells us that "they are being removed." There is no indication as to whether or not current premade characters will be moved to the new realm or just outright deleted.