According to the poll, 12 of 23 economists, said the government would not buy up the yen in order to stop the currency from weakening further. However, 5 respondents did note that if USD/JPY were to hit 150, then it would prompt intervention by Japanese officials. The other levels picked were 155 (3 respondents), 160 (2 respondents), and beyond 165 (1 respondent).
Sumitomo Mitsui's chief economist, Akiyoshi Takumori, said that the recent BOJ 'rate check' surprised everyone but intervention-signalling would be the "last thing" that the BOJ could do. While Sony Financial Group's senior economist, Hiroshi Watanabe, said that intervention is a possibility beyond 150 if the yen falls "at a very high speed" but in reality, it is extremely unlikely given the ineffectiveness of such a maneuver.
For a bit of history on yen intervention, you can check out the graphic on this post here.