After today's episode, I got a hunch that the second ending hints/flatly states who the other titans are.
Spoiler:
http://www.youtube.com/watch?v=sjKxEpeew_c <- 0:25 mark
Seeing how some anime like dropping hints on their Opening/Ending sequences, and how some people (myself included) already believe that Annie and Reiner are titans... Dunno. Could be a coincidence, but I don't feel that's the case