An increasing number of economists forecast that consumer prices will not only fail to meet the Bank of Japan's target, but that they will peak as soon as this autumn, in stark contrast with the view from Gov. Haruhiko Kuroda and his policy board.

Inflation will top out at 0.8 percent in the fourth quarter of this year, according to the median projection compiled by Bloomberg. With energy prices expected to be flat, some analysts see that coming even earlier.

In its crusade to raise prices, the BOJ has kept interest rates near zero for almost 10 years and has been buying bonds since 2010 in the current easing cycle. Kuroda doubled down on monetary stimulus in 2013 in an attempt to jump-start inflation. If after all that time, inflation peters out at less than half the target level, it may raise the question of whether the BOJ has reached the limit of what's achievable.