[quote=@DocTachyon]
<Snipped quote by Lord Wraith>

My assumption has been that the Titans here are more or less the Young Justice team that appears in the show, but with the Titans title.
[/quote]

It's left inherently ambiguous, as is the League. More of a 'cross that bridge when we get to it' sort of deal. 
But, it's a fair bet that the Titans are made up of every Protegé that isn't still a sidekick or dead.