Reuters reports, citing sources familiar with the BOJ's thinking
The report says that the Japanese central bank is to offer a brighter view on the economy, output and exports than in July in order to signal that they are recovering from the fallout caused by the coronavirus outbreak.
Adding that the BOJ should say that the economy is bouncing back after a severe downturn but will warn that any recovery will be modest and mired by uncertainty, as compared to their July view of the economy being in an "extremely severe state".
I don't think this comes as too much of a surprise but I reckon any upgrade to the economic assessment also needs to be taken into context, as the BOJ isn't likely to signal a significant shift in their policy outlook in general.
If anything else, there could be a minor tweak to their current views on domestic economic conditions but I wouldn't expect much else beyond that on 17 September.