It appears that Sony has all but abandoned the trademark for The Last Guardian.
A troubled development has cast doubts over the status of the title but it seems clear that things are a lot worse than originally feared. A user on Neogaf posted a link to a Trademarkia document which appears to confirm Sony has decided to let the trademark lapse.
Trademarkia cite the decision as “changed to ABANDONED – NO STATEMENT OF USE FILED”.
What this means for the title is currently unknown at the moment. We’ll reach out to Sony and see what they say.