In Mists of Pandaria there are two new world raid bosses (that we know of):
We also know that Blizzard is only opening up raids some time after the initial release of Mists of Pandaria (Source).
Will the world raid bosses be available on release, or will they be delayed like the normal raids?
Best Answer
They will be available upon launch.
Thats from a link in your source.
Edit: I'm aware that there is an ambiguity but as I understand it the world bosses are ready at launch.
Update: it has been 100% confirmed that "the two world bosses will be available at release day" in an MMO-Champion translation of an EU interview (original source at previous link).