Sony has abandoned the US trademark for The Last Guardian. They may renew it later, but at this moment, it seems like the trademark is up for grabs. This is not a new thing, however, as even Versus XIII was renewed later by Square Enix, so it remains to be seen what Sony does here.
Abandonment Notice! On Monday, August 6, 2012, status on the THE LAST GUARDIAN trademark changed to ABANDONED – NO STATEMENT OF USE FILED. Apply Now for this name starting at $159!
CAUTION: Although federal registration for this particular filing is inactive, the mark may still enjoy common law rights, or may have been applied for again in a separate application. Further research may be warranted to determine where this mark is truly abandoned in commerce.