Scott Miller of Bleacher Report is reporting that Petco Park will likely be the host of the 2016 All-Star Game. An announcement is expected to come in January.
As Miller noted in a reply on Twitter, this will be an odd instance in which one league hosts the midsummer festivities in back-to-back years -- the Reds will play host in July at Great American Ballpark for the 2015 All-Star Game. The National League also hosted in back-to-back years in 2006-07 in Pittsburgh and San Francisco.
According to a report as recent as last Saturday, Baltimore was expected to be the site of the 2016 All-Star Game. Though, in that report, San Diego was listed as one of the favorites to host in 2017.