Through this delay in full implementation of the law, miners will be given extra time to build smelters.

Positive impact of Mining Law No.4/2009:

Higher revenue due to value-added exports
Less dependent on volatile global commodity prices

Negative impact of Mining Law No.4/2009:

Disturbs trade balance and current account balance on the short-term
Law is not in line with long-standing contracts, causing legal uncertainty/lack of investor confidence
Small companies with small profit margins/small processing capacity may seize mining activities
Can lead to increased unemployment
Government loses revenue on the short-term due to declining exports

Further Reading:

Indonesia's Mining Export Ban Impacts on Current Account Deficit in 2014
Indonesia Might Delay Implementation of Mineral Export Ban by 3 Years
Indonesia May Review its Ban on the Export of Unprocessed Minerals
Go-Ahead for Indonesia's Controversial Ban on Unprocessed Mineral Exports
Indonesia Studying Temporary Exemption for Export of Raw Minerals
Export Ban on Unprocessed Minerals Temporarily Pressures Trade Balance