It is unlikely that the BoJ will leave matters as they stand after today’s rather insipid developments. If the market insists now on testing their resolve, traders expect the BoJ to enter the market and buy USD/JPY at 84.00, at the latest.
That’s why the bigger hedge funds have placed their bids at 84.50 and below. I’m guessing their motives of course, but the first wave of intervention is often the most successful so the big players try to get on board for that and make a quick profit.