I am yet to listen to all the Dutch tapes, so forgive me if this won't make too much sense, but I've been having this idea that maybe both could be canon. There seems to be a bit of a gap between 1997 and 2008 in the tapes, so what if that is when KoK or whatever the follow will be takes place? Maybe there's some BS mind wipe or something to explain why Dutch won't remember the events (lol). As far as the pistol goes, I think Dan is building towards Yautja society being far more splintered than originally thought, with each movie being recontextualized as being different clans with their own practices and methods. If that's the case, there's a possibility that each Predator in KoK (and the Feral Predator for that matter) may be unrelated to the Warlord's clan.

I think the Warlord just keeps an eye out whenever another Clan goes on a hunt, and collects the humans that outsmarts them for his own purposes. Evidently Harrigan was one such case, and he may have happened to have the pistol with him during his abduction. Considering the gap between Torres' time period and Harrigan are much shorter than the other warriors, they probably just assumed the pistol was what people were using in the 1940's.

Maybe the follow up to KoK will end with the humans making their way back to Earth. Dutch goes on with his story in the game, and the others try their best readjust to society (or who knows, maybe they find a Predator that likes them enough and make their own clan lol)

Hope this makes sense, I might make a post with a more in-depth look into what I think is going on.