I would say that it is not new. There is actually a large amount of highly literary SFF, but it's mostly ignored, by readers and critics alike. It has always been there, and there continue to be writers who write it vociferously, but they are not being bought. Two of my critique partners write astonishing literary sff; agents won't touch them. That devastates me, when I think that their novels might never see a shelf.
A few break through, like Gene Wolfe and Le Guin and Zelazny (ahh my heart) to enthrall even critics + find success, but Wolfe is very old and the other two (obviously) are dead. Neil Williamson, Caitlyn Kieran, China Mieville, Nnedia Okorafor and others are part of the modern lit fa, but few of them find wider recognition (and honestly, I struggle with calling Mieville 'literary' but that's another discussion entirely). It is a tough thing to write literary sff atm. Nobody really wants it, nobody really knows how to cope with it. And nobody can agree on whether it is really "literary" or just prettily written. (Some would call Neil Gaiman literary, for example; I would say he is borderline. Subjective, innit.)
I've noticed an uptick in contemporary novels which have a smidgen of speculative element (Kazuo Ishiguro, Emily St John Mandel, and so forth) which are lavishly adored by critics and reasonably successful in the mainstream, and I must admit I find that frustrating. It suggests to me that literary and SFF can only typically be seen to merge when the setting is contemporary, thus excluding secondary fantasy or far future SF. At least readers are more accepting than criticis I suppose.
I could not comment on HP one way or another, since I appear to be one of the 0.005% of the population who hasn't read it >.> Magic schools are not my thing, I avoid that trope in anime too.
Anyway, I digress. Apologies.
