I'm pretty sure arresting on return and arrests for helping people to leave the state are already happening.

It's certainly close enough that there are preemptive reports asserting that it would be federally illegal: https://www.reuters.com/world/us/us-justice-department-says-constitution-protects-right-travel-abortion-2023-11-09/

The Alabama lawsuits seek to block the state from criminally prosecuting those who facilitate out-of-state travel for an abortion. Alabama Attorney General Steve Marshall has said those who aid travel can be charged with conspiracy if the out-of-state abortion would have been illegal in Alabama.