After numerous major and minor setbacks, The Last Guardian is still alive, but Sony let the license to expire (again). This movement could indicate that the game is no longer in development, but Sony have confirmed that the game is not cancelled.
On February 16, The Last Guardian trademark expired due to an “administrative mistake”. The company forgot to present the verification for the brand. On February 17, Sony renewed the brand.
To sum up, the brand was abandoned by mistake, renewed and the game is still alive.