I don't think Brunel will respond voluntarily. They are too stubborn and set in their beliefs, and it is not being forced on them, but they feel it is one independence they gained when they gained their independence from New Zealand. Many of their laws are due to their religion, so it would be like asking or telling them to change their core belief system.
I think if it changes it will be a matter of force, and that seems highly possible at present. How much force and what kind of force remains to be seen. Oddly enough, it is the other Islam nations that are having the biggest problem with their version and implementation of Sharia law, and most of them have the law too, just not to the same degree.
Brunei will not respond to international pressure in a positive mode. They will defend their choices and uphold the decision to adopt the new penal code. Human Rights Watch International said the rollout of Brunei's new Sharia criminal code poses "grave threats to basic human rights." It was reported that the system is primitive and imposes archaic punishments.
Amnesty International requested that the international community raise a voice against Brunei’s decision by stopping business with them. In response to the outcry, the Prime Minister stated that the penal code would maintain peace and order and preserve religion, life and family values to this country.