I'm ignorant. What does this mean?
That they're working on some un-named content for PC (Dragonborn) and PS3 (The previous DLC, doubtful DB will get on PC3).
Probably due to legalities/commitment issues they're not allowed to say the actual names.
Because if they don't release DB, or any Add-ons for PS3, "content" could mean an update and no promises (based on that tweet) would be broken.
Reading the thread about DB beta, it seems there are some PS3 users in the Beta. Not sure that means there /is/ a beta for PS3 (very unlikely) because I believe the 360 beta testers were chosen at random.