Ruin Explorer
Legend
Based on market position, it is facing a much bigger challenge than 4E with PF already firmly in place plus a fair number of 4E hold-outs. 4E clearly was a master at providing a certain game niche and people who love that niche are well justified in staying there.
I dunno. I think a lot of PF players who were new to PF and really hot about in the 4E days are pretty tired of it or have already moved on to other games, now. There is a hardcore PF-only fanbase, but it's small and loud, not large. With 4E, it's a bit different, but I think there are lots of 4E players/DMs who are ready for another iteration which doesn't entirely screw up stuff they liked from 4E, and which does have other cool stuff. 5E could be that latter.
So I think whilst there may be a lot of semi-entrenched people, it won't face the same sort of "hot" or "aggressive" resistance 4E did (in part because of it's dumb-arse "ur game sux" marketing at the beginning).
Also, hype-wise, 5E is getting WAY MORE hype than 4E did outside the traditional RPG sphere. Far more coverage from mainstream media outlets, from general or even computer-game-specific gaming sites, and so on. It may be behind in the actual RPG sites, right now, but I think way more people in the world who might play will learn about it.