Given the gloomy outlook for global economic growth, the Bank of Japan is expected to keep its current interest rate levels at -0.10% and extend its monetary policy to the first quarter of 2019. It is more than likely that the effect of the decision on the Yen would already be priced in before Friday, however, any major and turbulent spikes can be resulting from the statement of the BOJ itself.
Given the recent remarks by the Reserve Bank of Australia, the Bank of Canada and the European Central Bank, which have all stated the trade tensions between China and the US and the limited trade negotiations on a global scale as the prime concerns over the reduced expectations for global output in 2019. Consequently, those circumstances led to the dovish policy stances for all of these banks.
Because of the direct dependence of the Japanese industrial sector of trade exports to both China and the US, a main focus of the statement would be the BOJ's account on inflation rates and its expectation for economic growth in 2019.