You see, putting the PS3/PSN logo there would effectively force them to release the DLC to PS3. Bethesda don't want that. They want the option to bail out at any possible moment, and they are taking precautions to make that possible. They didn't give us a certain release date so that we can't use the argument "oh it's not out when it's meant to be"; they didn't include the PS3 logo so they don't HAVE to give the DLC to us... you get the general idea.
They don't want to be in the situation where they HAVE to give us the DLC.
Although the 'PSN' logo thing is a bit of a red herring... It did set me thinking as to why they should, in all honour, 'HAVE' to make some effort to produce DLC for the playstation. In the lead-up to Skyrim's release, Tod Howard, Pete Hines, and numerous other Beth. luminaries quite happily appeared at conventions, and in many media outlets, describing the 'large' expansions that purchasers of their game might expect. "Bigger than Fallout", was I believe what was promised. For myself, this was not a small consideration when I forked over my money for Skyrim... some outlay up front, but then at reasonable intervals, more stuff to keep me amused for about the price of a film ticket. As things stand however, I find myself in the position of someone who, pardon the comparaison, bought a car with an 'extended powertrain warranty' but was then told that, no, they wouldn't fix it, because I'd gotten the red one, and that wasn't their preferred colour.
If, as near as I can tell, the supposedly horrific technical hurdles in producing a small DLC for PS3 are in fact fictive... and I have heard no reasonable explanation to the contrary (seriously... adding a half dozen new animations will crash a system that quite happily runs 'Red Dead Redemption', or indeed post 1.4 base Skyrim with less lag than X-Box... or save-file bloat issues are any worse than in any previous Beth. game), I can only assume that for reasons related to their return-on-investment Bethesda have decided not to hazard resources on any further PS3 content. This may make sense for them number-wise... but it also makes them guilty of false advertising.