Latest DLC, 'Dragonborn' a priority over 'Hearthfire' and 'Dawnguard.'
The PS3 version has, among other things, an issue where the more the player plays the game, the worse the game's performance gets depending on a variety of sub factors that the game's open nature allows.
These performance issues have been the subject of controversy and frustration. Unfortunately, the continued absence of DLC for the PS3 version is not helping the situation.
In a post on Bethesda's blog discussing 'Dragonborn,' the following statement was directed towards PS3 players, "(W)e’re hard at work to make this content available early next year on PS3 and PC. On PS3 in particular, we turned our attention to Dragonborn, as we thought it was the best content to release first, and we didn’t want folks to wait longer. Once it’s ready to go for everyone, we’ll continue our previous work on Hearthfire and Dawnguard for PS3. Each one takes a lot of time and attention to work well in all circumstances and all combinations of DLC. Once we have a better idea of release timing and pricing, we’ll let you know."
'Dawnguard' was released on the 360 in late June and on the PC in early August.
Source: Bethesda Blog via Kotaku