As stated above, I will ask to find out if this is possible from a legal sense.
In addition though, I do want to point out that the Kingmaker 5e Monster Manual and PF1e Bestiary are just monsters to use for parts of the game. There is no mention on how to convert other aspects of the campaign. If approved, the best I can offer is to make sure the adventure runs in the other rulesets. There will be no official conversions to replace Pathfinder 2e rules with PF1e or D&D 5e rules. It will be up to each GM (PF1e) or DM (D&D 5e) to modify the rules to fit, which will be some work by the GM/DM running the game. So in summary, the basic story can potentially be there but the specific game mechanics will have to be evaluated/replaced by each individual GM/DM running the game.
I should also add that making the story compatible in other rulesets (if approved) is not a high priority item and will happen after the other items on the roadmap.
Hope this clears this up.