Unknown? Seriously?
You do realize that Titan's development is long plagued with fanboy bitching about taking away WoW's "A Team" of developers to work on Titan, right?
While I cannot recall the details right now of how both were covered in share holders meetings, Destiny was just officially unveiled. There is not one mention of Blizzard involvement at any step in the process.About the share holders. Im pretty sure nothing has been said about what Bungie was working on in those meetings so why would anything about titan be said either.
Not to mention there was that 27 page contract between Bungie and Activision, which also made no mention of Blizzard, that went into effect in 2010 at the latest and we have still been getting assurance from Blizzard after that time that they are still working on Titan. And none of the leaks that people hold up to such grand praise have hinted at such a huge change in development (not that this proves anything in my eyes, since I think all the leaks are bunk, but your theory operates on the "Titan = FPS" leak so you must hold them in higher regard than I do).