Logan: 7 Ways It Sets Up A Sequel
3. New Mutants
Not to be confused with Josh Boone's forthcoming New Mutants movie, but rather a film built around the new mutants introduced to audiences in Logan.
Although we don't get to learn a great deal about these kids beyond Laura/X-23, we see enough to know that they have a wide-range of powers, from Rictor's seismic abilities to being able to manipulate grass (and potentially more of nature).
With these being the last mutants (that we know of) in this timeline, there's a possibility that Fox would decide to make a movie focusing on their further adventures - and in fairness, it's not like they don't have the groundwork prepared.
As mentioned, Transgien is still out there, the kids are headed to Canada, and Dafne Keen, who plays X-23, is going to be in-demand for more X-Men movies. This would be one of the easiest ways of continuing and developing the new arcs and characters established here.