The Bank of Japan is certain to raise rates further. The question is when

The Bank of Japan is widely expected to stick to its monetary policy tightening campaign as inflationary pressures in its capital city of Tokyo reaffirm the bank's economic projections. But market participants remain divided over the timing of the next hike. 

"My money is on another rate hike in October," Stefan Angrick, senior economist at Moody's Analytics, told CNBC via email. He predicted that hike would be followed by at least one more in 2025, possibly as early as January. 

Japan is likely to continue seeing "jumpy" inflation in the near term, Angrick said, noting government efforts to trim energy subsidies. While Prime Minister Fumio Kishida has pledged to extend support for household utility bills, he acknowledged these measures "cannot continue forever."

Kazuo Momma, a former BOJ official and currently executive economist at Mizuho Research & Technologies, however, expects the central bank to keep the rate unchanged in October. His base case includes a hike in January to 0.5% and a further hike to 0.75% in July. Momma said that would take Japan's monetary policy to its final position in this tightening cycle.

On Friday, data showed headline inflation for Japan's capital city of Tokyo accelerated to 2.6% in August from a year earlier, faster than a 2.2% climb in July. The core inflation rate, which strips out volatile costs of fresh food, rose 2.4% from a year ago. That's faster than the median market forecast and the July reading of 2.2%, accelerating for the fourth straight month.  

Still, Momma said "the momentum is not strong enough" yet for the BOJ to hike rates. As the central bank monitors global financial market risks, he said the BOJ does not "have a good reason to rush at this moment."

The upbeat monthly CPI data are affected by recent "policy flip-flops," Moody's Angrick said, referring to several counter-effective policies at play. He explained the government provides some subsidies, while dialing back other support measures. That, in his opinion, shows "a reluctance to provide effective support."

Demand-driven price pressures have remained subdued and employment conditions are softening, Angrick said, noting that the upcoming Liberal Democratic Party election adds further uncertainty to the future policy course.

Japan's jobless rate in July also rose to 2.7%, up 0.2 percentage points from June, according to government data published Friday. Economists polled by Reuters had expected July's unemployment rate to come in at 2.5%.

"At best, additional rate hikes will be an added drag on growth," Angrick said, "at worst, they could precipitate a broader downturn." 

The Tokyo CPI is a leading indicator of nationwide trends and has been ticking up as wages rise nationwide and the government tries to phase out energy subsidies, alongside a weak yen.

But the underlying inflation should fall below 2% over the coming months, Marcel Thieliant, Capital Economics' head of Asia-Pacific, wrote in a client note.

The BOJ surprised markets in July by raising interest rates to 0.25%, a 15-year high, and outlining plans to scale back its massive bond buying program. 

BOJ Governor Kazuo Ueda recently told parliament the central bank is ready to hike borrowing costs further if inflation continues to rise above its 2% target.