Today a post (see the link below) was made on the Progressive Ears music forums, with a roster of US dates for this year's Summer/Fall tour. One might take them with a grain of salt except that we do know at least two of them have already been confirmed, so I'm likely to believe it's a promoter's leak of some kind and they are correct. As well, the geographic spread and number of dates seems entirely in keeping with previous tours. Hopefully this means an official announcement is forthcoming either this week or the next.
http://www.progressiveears.org/forum/showthread.php/22060-Yes-(ARW)-2018-50TH-ANNIVERSARY-USA-TOUR