Update 7/4/2018: The website linked in this article has been updated with a date of 9/28/2018 as a release date. I guess this got someone’s attention at mophie.
Always on the lookout for new accessories from mophie, I stumbled across this Australian retail page showing a possible release date of 7/13/2018 for an iPhone X mophie Juice Pack Air.
I am not sure how reputable this site is but this could be an indication that we will see the new case from mophie this month.
I will update this as I find out more.