This trademark registration is a completely new filing. A previous trademark registration for Deep Down, which was filed in July 2013, is still valid. That trademark had its fifth extension granted in August 2016.
The last time we saw something new from Deep Down was a set of screenshots in December 2014. Then, in February 2015, Capcom producer Yoshinori Ono hinted at the game changing course and growing “much larger” than originally planned, saying that “it might be a while ahead, but we hope to show you something truly different from what was shown previously.”