I don't know if the number of PF players and games has gone down, or whether there's been enough of an increase in D&D 5 to just overtake PF, so the actual number of PF games may not have decreased at all. From what I can see D&D5e has been part of an explosion in visibility and popularity of RPGs so overall Paizo and PF may have benefited, only from what I've read and seen, I don't play any flavour of D&D of which PF is one. As far as RQ goes I now play Mythras on roll20 as the RQ6 character sheet still works. From what I know of some of the authors of various version of D&D, the influence of RQ got felt at least a little in even the official D&D rules. RQ has a rep for complexity but I blanch looking at some of the PF rules, playing it must seem like sitting under the apex of an inverted pyramid, learning RQ is more like Enemy at the Gates, huge attrition but if you survive you'll be wiser. Mixed metaphors, don't use them.