The Black Desert Online team has posted a brief note to let players know that the Siege System is yet again delayed. It appears a pair of "problematic" bugs have cropped up that prevents deployment of the anticipated system. There is no estimated time on when these issues will be resolved or when the update will be released.
With the first week of Siege Rehearsal almost complete we would like to thank all of you that have been participating and reporting the various problems as well as sharing your feedback. Unfortunately the two most recent bugs have proven to be problematic, one prevents siege towers from receiving damage while the other prevents guilds from building towers on time. Due to these bugs, following the Region Siege War this Saturday we will be postponing further sieges until we have a patch to correct these problems.
While this delay in siege content is not ideal, we do this in order to address the problems as quickly as possible and insure that all guilds have an equal opportunity to participate and enjoy this system.
We'll keep you posted as the story develops.
Source: Black Desert Online forum