Pointless meme debate. No one can be the 'next' Miyazaki because he (probably deliberately) never created any successors. In the first place, he and Ghibli in general are anachronisms, the way and type of work he does has barely changed since before the studio itself was even founded. The industry won't (and can't) support the existence of that kind of approach without someone whose name is already guaranteed to sell and can attract the necessary talent. What other people like Shinkai are making isn't the Ghibli formula to begin with, so it's also stupid to assign them a role as "successor" arbitrarily, it's as empty as marketing-speak.
This shit probably only keeps being spouted because Miyazaki is "the" director in the eyes of every clueless idiot who heard about him from the time (((Disney))) bought him a slot at the (((Oscars))). Look forward to way more of this than usual if that ever happens again, regardless of who it is.