Batman on Film came with this scoop and, while the site had quite a few rumors that proved to be true, this should be taken with the usual grain of salt. It appears that the first teaser trailer for Batman v Superman: Dawn of Justice is already done and that it will be first viewed with one of this fall’s movies. Most likely, it will be featured before a November or December release.
But, given the release date (25th of March 2016), isn’t it too early? Just asking.
Anyway, the same website reports that it will be a Batman-centric teaser trailer.