SQL statements won't change, but the surrounding code will. Any code that refers to the database will have to be updated. That includes connections, recordsets, loops, inserts, updates, and display code.
We will have upgrade options in the new version of databridge, so when you open an existing server behavior and switch from a mysql to a mysqli recordset the associated code will be updated. But it won't work for custom code and will have to be done for all server behaviors individually.