No. It is not going to benefit the country. On the other hand, the situation will deteriorate. The law and order will collapse, and the poverty will worsen. If Duterte want to eradicate drug usage in Philippines, then he might need to exterminate up to ten million Filipinos. The easier option is drug legalization and regulation. But at this point of time, I don't think that he will consider that step.
Why would you legalize a drug that can damage your brain. This will not and never be an option. Many innocent victims and crimes are related by drugs. This crime will just go up if it will legalize.