According to this: Wow server stats
Wow had something around 1million active characters in last week and around 550 servers.
Im just assuming that it means that the server population limit will be around 2-3K.
Keeping that in mind:
Until now Bioware listed 106 servers - 10%of them is full, 10% is High, 70% is on medium and 10% on low.
I would assume that they will be inviting around 250-300K players per day.
Which leaves me with my pre-order dated 2nd of December at the very end of this long queue.