I wouldn't say they've become less efficient, I think it's more likely the reason why things are taking forever is that they're building new engines to base games off of, which takes forever, and afterwards we'll see wave after wave of exclusive, just like what happened with PS3.

I'm putting my money on that they have taken over the Killzone franchise.
We know they're working on a PS4 game and we also know they are working on 'a high profile, multi-million selling franchise', and they adopted the Guerrilla name and already made a Killzone for the Vita. I'll be shocked if they aren't working on a new Killzone game.

It's never just a single game with those guys though. Don't forget they've just co-released Order 1886 and have a new Fat Princess game coming out.

They are working on some big multi million selling PS franchise (I.e killzone)

Sony Bend finished Uncharted Golden Abyss for launch in 2011. So they've been working on that since then, without any information?

Sony London did the Getaway and 8 Days. I want those games back! (and an extension to the Getaway's London map by a few "blocks" so my house is in it). Note in this case wikipedia says they're working on "street luge" for project morpheus

There have to be serious issues if they worked on a new IP for 3 years and then had to cancel it

Again, Gravity Rush came out nearly 3 years ago

This productivity is just really unimpressive. But I really do think they're having problems with devlopment. When the Last of Us was announced, Naughty Dog said they were a 2 game studio. Uncharted 3 came out in 2011, which means they'll have taken 4 years over that game, which is clearly not what they planned

Either Sony have cut all their workforces, or they're all really struggling to make quality games. Especially given that none of Sony's next gen exclusives have been that remarkable (I would say Second Son/First Light were, but I think I'm in the minority there)

I'm going to assume it's Killzone.

Sony Bend also released the smaller turn based card game Uncharted: Fight for Fortune for the Vita at the very end of 2012. If they're working on a PS4 title, they probably needed ~2 years from that point (full staff on board) at least, to create the concept, build an engine and and begin hiring as they hit full production. We're probably looking at a mid to late 2016 release for their title. Which would be a rather normal development cycle of 3.5 years for a first release on new hardware from a smaller development team. Yoshida described the game as 'panic' in one word and it's been rumoured as both an action/adventure and a open world horror.

London Studio are probably a lost cause- they will most likely continue to develop casual software.

Well, the new IP was in the hands of a veteran (Stig Asmussen) and had a tentative 2013 reveal attached to it. According to rumours though it failed every Q&A, went through constant re-design and Sony had blown millions before they finally pulled the plug (similar to L.A Noire). 

In terms of productivity Sony have indeed released less PS4 titles in the same timeframe as they did with the PS3. That follows in line with their statements regarding less of a focus on medium sized releases. A title takes as long as it does to make -3-4 years usually for a good release on a new platform. You can't rush it, you can only strategically stagger development and try to time releases to fit into a schedule that will ultimately push the most hardware. 

This gen they opted to push Sucker Punch and GG to get titles out early. Both spent over a year less in development on their games then they did on their first PS3 projects. (Which could tie in to why you think they aren't as remarkable). Evolution dropped the ball on Driveclub and took longer.

there was a rumor from tidux though, that sony bend worked on another vita game for a year, then sony axed it due to low vita sales. however, i wonder if thats true or not.

also, RaD released their last PSP game in oct 2010, and released their next game the order in Feb 2015. thats 4.5 years of dev time. my point is, bend is in a similar situation, they were making handheld games and moved on to console, that transition takes time.

sony london havent made anything big or AAA in a long while, so no reason to assume they are moving back to AAA games, even if they were, we have no proper way of figuring out when they decided to start making AAA games again. 

also, naughty dog never said they were a full two team studio. after UC3 a small team started UC4, most of the studio went on to work on TLoU, same thing happened after TLoU released. if ND can pump out a new game every 2 years, then id say they are hell of a lot effiecent. 

as for gravity rush, we really dont know whats going on, if they decided to move the game from PSV to PS4, that would explain the delay, and im sure they would want to use the PS4's potential rather than keep it on the scale of what is was going to be on the PSV, that would take time, wouldnt you prefer they take their time for that reason? 

i agree, Sony's efforts so far on the PS4 havet been great, but 2015 seems to be on the right track, and things seem like they are getting better and better. the first year of a new console isnt really the best to judge.