Doesn't Riker's promotion mean the end of Star Trek: Titan?
Not necessarily. DS9 didn't end when Sisko or Kira left the station (though Sisko's around quite a bit anyway), so why would Titan
end because Riker's moved up in rank? I agree with those who see Riker taking the vessel as his flagship (much as Kirk did during TWOK and Riker himself did during "All Good Things...") and remaining in command of the vessel until a permanent replacement can be found. OTOH, why not have Vale move up and take the center seat? Or maybe this is finally the opportunity for Worf to have a command of his own?