Even now, I still see people speculating on Titan and "The Dark Below". All of this has been confirmed people!
Titan = The MMO - Destiny. When Blizzard "changed teams" or "wiped the slate" as some people have stated... They DID change teams.. but not within Blizzard. It changed from Activision "Team Blizzard" to Activision "Team Bungie".
Classes on Destiny: TITAN, Warlock (with their awesome voidwalker ability), and Hunter.
Confirmed 1st expansion of Destiny that is now listed on their website under the "EXPANSION PASS" section: The Dark Below.
Hopefully this helps end the speculation out there