The BOJ is reported to likely offer some form of numerical guidance to markets on how much JGBs it will continue to purchase, upon ending negative rates and its yield curve control (YCC) policy. The sources say that as the BOJ makes an exit from negative rates, it is also likely to scrap its YCC policy as well. Adding that:

"The BOJ would have to keep buying government bonds to some extent, and present some form of guidance to avoid any abrupt spike in yields. The bond buying will likely be used as a backstop against unwelcome spike in yields."

Another source noted that the Japanese central bank could set a loose quantitative guidance as among its options. And that they should roughly maintain the current bond buying pace even after scrapping YCC.

For some context, the BOJ currently buys around ¥6 trillion worth of JGBs per month in order to stick to its yield target.