For one thing, Jason wanted to make some improvements to his model. After he finishes it, VSTEP have a considerable amount of work to do getting it into the game, including the dynamics and the new controls.
Titanic is a very high poly ship, and caused many problems in SS08 during environment changes.
Given the present state of SSE with its already high memory and processing demands, introducing Titanic at this time would probably be a big headache for technical support.