Been a long time since a book had any GP impact after Harry Potter but if there's one,what do you think would it be?

Can't predict it if it doesn't exit

Post-Potter we've had twilight, hunger games, and fifty shades.

None of those had that GP impact though.

They made tons of money with both books and movies, so your question doesn't make any sense then and there isn't a possible answer.

A song of Ice and Fire, I see many people have started to read the books ever since the abomination that was season 5.

I think he means that they hadn't had a thoroughly defining pop culture impact like Harry Potter did. From things like midnight releases for the books (I've done this for Harry Potter books starting with Goblet of Fire), literature courses in college etc.

Sure the other franchises made money with both films and books. But they weren't really everywhere like Harry Potter was. And the audience for them were primarily teenagers (unlike Harry Potter's universal appeal).

I honestly don't know any book series that are post- Twilight / Hunger Games / Percy Jackson. ASOIAF technically predates Potter, even if the TV show does not.... Anyways, I can't really say what will "happen" next. I guess you could check to see what book series have had the film rights purchased...

As for standalone books that aren't part of a series, John Green's Looking For Alaska is supposed to be getting a film adaptation soon, so that could increase its popularity a bit.

On Amazon, the collection was #97 in books for 2015, #34 for 2014, #23 for 2013. While not bad, not an omgphenom the way the show is.
(#15/#56 for the first 4 books collection/the 5th book in 2012.)

Compare to, say, Fifty Shades which was #1, #2, #3, and #6 in 2012.

I don't think A Song of Ice and Fire really counts since it's part of Game of Thrones anyway...regardless, I literally have no idea. Harry Potter was the last real BIG book phenomenon, Twilight, The Hunger Games etc kinda fell short and no book has really had the same impact.