New details about what is happening with Dawnguard and Dragonborn have come out for owners of the PS3 from Pete Hines. He was asked for an update about the two DLC packs and said that work was still going on and that Bethesda were committed to releasing Dragonborn. The full comment is:
We were still working on Dawnguard. We have committed to Dragonborn release. Just haven’t announced date yet
At the moment only owners of the Xbox 360 have Skyrim Dawnguard, Dragonborn and Hearthfire DLCs. PS3 owners should look ahead to a great busy year in regards to DLC. Bethesda have said that owners of the PS3 will get Dragonborn first and they are working on Dawnguard along with Hearthfire for the PS3.
The PS3 release of Skyrim DLCs have been delayed due to technical issues which have caused problems with performance. Both Bethesda and Sony have worked on issues over the past several months and they have shown commitment to getting the DLCs out to PS3 owners.