The real interesting question is what PF2 would look like if 4E was still going? After that, will D&D ever go deeper into 4E design now that PF2 is rolling with the ORC?
I suppose in an alternate reality where everyone who hated 4e enough to engage in edition warring died of apoplexy (because we're just that old that we don't say coronary thrombosis, nor even heart attack) upon glancing at it, and Hasbro, while disappointed with it's sub-MMO revenue, let it linger on in some slow-release life-support mode until Stranger Things &c touched off the come-back, (newbs showing up expecting to roll to hit with a fireball would not be disappointment), and the Pandemic finally brought VTT adoption up to the levels it needed.... well, you might not have had a PF1... and if you did, PF2 would presumably have continued in the same vein of "more D&D than D&D."
OTOH, if the alternate reality 4e does OK because they just put out an OGL with it and kept Paizo on board, there'd definitely have been no PF1 or 2.
OTOOH, if 3.5 had been allowed a full dignified run of 10+ years like 1e, the fanbase might have been ready for a radical change with the next edition, and, coming out closer to the right time, 4e might even have met it's unrealistic goals ... by 2016 or so.... Tragically, tho, a 4e with exclusionary GSL timed to the come-back could have succeeded in driving the (now tired, 12+yo) OGL/SRD and 3pps sticking with it into the ground... and, alternate evil-genius Hasbro could then kill Paizo at whim... so no competing PH1...
(...I just can't do a nice alt.history... it's not in me, somehow....)
Either way, tho, the 50th anniversary edition would, I'm sure, be a
different edition, not a timid don't-rock-the-boat nominal revision, as WotC would be equating success with radical change instead of tradition.