http://kotaku.com/what-happened-to-the-last-guardian-1711835457
Yoshida said that when the game was announced in 2009 for PS3, they thought they were making good progress.
“But in 2011 the progress became super slow. There were lots of technical issues. The game was not performing at speed. The video we showed, the trailer on PS3, was specced up. The game was running at a much lower frame rate. Some features were still missing.
“So it was clear that the team had to make a compromise in terms of features and number of characters so while they were taking time, the engineering team ported the code on the SPU [processors of the PS3] to improve the performance, but it was taking lots of time.
“But, in the meantime PS4 arrived, the development environment was available. So in 2012 it became apparent we should move it to PS4 to achieve the visual [ideal.]”
Yoshida said that the rumor that veteran game designer and programmer Mark Cerny had been brought in to save the project were incorrect. “Mark has been consulting many of the first-party teams and projects, giving advice on the tech side—not just him but other central tech groups we have from the U.S. and U.K. have been helping the team as well.”
Some notes aside from what is on the title
Fumitu Ueda kept working on the game normally even after leaving Sony
Technical restraints kept it from shipping on the PS3, same as what happened with ICO:
"After two years of development, the team ran into limitations on the PlayStation hardware and faced a critical choice: either terminate the project altogether, alter their vision to fit the constraints of the hardware, or continue to explore more options. The team decided to remain true to Ueda's vision, and began to use the Emotion Engine of the PlayStation 2, taking advantage of the improved abilities of the platform.[17][18] Character animation was accomplished through key frame animation instead of the more common motion capture technique.[19] Ico is recognized as one of the first games to incorporate bloom lighting into video games, a feature that is common in later seventh generation console video games.[1] The game took about four years to create.[4]" (Wikipedia)
