"We have tried a number of things, but none of them solve the issue enough to make Dawnguard good for everyone. The PS3 is a powerful system, and we're working hard to deliver the content you guys want."
In a forum post, an administrator said that the dev team was "not positive" the problem could be solved. This, omniously backed up by the statement; "Dawnguard is not the only thing we have been working on, so the issues of adding content get even more complicated." Perhaps, after the PS3's multitude of bugs in vanilla Skyrim, that could be it for the system's relationship with TESV?
So, it seems that Bethesda have got a big problem with Dawnguard on Playstation, so some of you are going to have to wait longer. Hopefully this will be made good by Hearthfire coming to PS3 in good time - let's just hope it gets there at all!