it's a tighter loop than what you describe
deporting people faces these hurdles:
1. identifying what country a person is from
2. getting a country to agree to take them
3. paying for the huge cost of mass #deportation
so your "they will replace #migrant #labor with #prison labor"
is more exactly
"they will remove migrant labor, imprison them, then put them right back in their old workplace paying them far far less"
that's their insidious game