There are two unannounced Marvel/X-Men films scheduled for 2018, though their dates has now been reshuffled as part of Fox’s updated release slate.
In addition, Fox has moved the mystery Marvel/Fox movie that was previously scheduled to arrive on July 13th, 2018 up a couple weeks to June 29th that year.
Which is of theses movies will follow right after Wolverine 3, however, has yet to be officially announced by the studio.
So again, the 2018 release dates are seemingly being reserved for those two movies.