Without knowing the details of individual contracts it's, of course, impossible to say what happens in these situations.
Sometimes clubs have an option to extend, sometimes a player earns an option to extend, sometimes there can be weird clauses.
With overseas players like Efford there may even be some creativity needed to ensure work permits etc are granted.
Sometimes, like Turnbull, players sign extensions knowing they are moving on but working with the club to generate extra revenue.
Regardless, it looks like SK has been doing a good job of slashing our inflated payroll.