I'm a reluctant user of GraphQL. I can't specify any deep technical reasons, I just prefer a lot more control over interfaces - particularly where I'm in control of both the client and server.

But. I use GraphQL. GraphQL is a whole toolchain around client-server interactions. (IMHO) It's a pain to get started using is, but then the benefits of tooling start to compound.

HTTP2 won't replace GraphQL. Perhaps a set of libraries that use HTTP2 effectively. Even then I'd be surprised if it was a huge departure from GraphQL fundamentals - but you never know.