I think if BGS announces their new game anytime during the first 4 months of 2015, we are probably still good for a 4th quarter release. While Skyrim was announced December 2010, they really didn't show anything other than a nicely rendered rune wall connecting Tamriel lore with the premise of the game. It was two or three months before we saw any in game action. Todd Howard has stated they would not announce anything about their new game until they really had something to show. (German interview in May or June this year if I remember right).
During that 11 month period before the Skyrim release it seemed to me that the forums got pretty snarky at times, as people started dissecting the game based on whatever limited info was released ( look what we do during the current vacuum). While I don't think it impacted sales in the long run, it's kind of hard to spin a positive promo, when the critics are constant; the social webs are quite immediate. To me a concentrated marketing push might make more sense, say 4-5 months long. Less distractions for devs who are finishing up and those leading the official hype train. I'm also speculating that a larger effort is being made to reduce the bug count at release. They took it on the chin with the PS3 problems, which meant re-budgeting to rework the game product already released as opposed to profit generating DLC.