One wonders if other authors would pitch on NF with the current situation?
Doubtful. The pro authors aren't usually burning to use other authors' original characters. They are more likely to be busy creating their own. If PAD announces he's officially done with NF, then it might happen, but PAD is already on record as willing to do more. If asked.
More likely, perhaps: PAD might get asked to pitch a "Typhon Pact" contribution for his next NF.