This is not really a question of history, but of current science.

"Is an exploration imminent?"

The article itself states that exploration is not going to happen.

And to those fantasizing about personally exploring the void, a word of caution. No known corridors connect to the space, and researchers and outside experts alike stress that there are no future plans to drill into the void. Instead, they say that in the near-term, they will do whatever they can to peer into the space non-invasively.

“There’s lots of heavy, thick rock, and by drilling something, you don’t know how you will affect the entire thing,” says Ikram. “If there’s something behind the Mona Lisa, would you want to wipe her clean and see what’s behind her? You really have to preserve the integrity of the monument.”

Another article mentions that the ScanPyramids project actually found two voids. The other, smaller void is close to the perimeter wall of the pyramid, and may be possible to explore with very small robots.

The larger void will have to be "explored" by continued muon scanning. The longer they do it for, the clearer the picture becomes.

"Has it been quietly debunked?"

No, this is not fringe science. The Nagoya University in Japan, the High Energy Accelerator Research Organization in Japan, and the Alternative Energies and Atomic Energy Commission in France all sent teams to verify the results, using nuclear emulsion plates, a scintillator hodoscope and muon telescopes, respectively.

We will have to wait until the ScanPyramids team releases a new paper with their findings. Until then it's all guesswork.