Yikes. You got me there.
Allow me to clarify a few things:
If Lego were to ever release a Minas Tirith set, it would come out in June 2016 at the earliest, as we already know all of the winter sets for next year. That would be exactly three years after the final Lotr wave hit the shelves, and two-and-a-half after the final production run.
Lego has not done anything to promote Lotr from June of 2013 until now, and even now the interest is fairly low compared to other dimensions themes. Other themes are brand new, such as Doctor Who and Midway Arcade, while Lego chose to rehash three Lotr characters for their "new" "sets".