I think QUIC is gonna be it, at least for the next 10 years.
It has unreliable, unordered datagrams, and a huge number of TCP-like streams, all wrapped in the same TLS'd connection.
When I look at QUIC, I see old TCP protocols like IRC and telnet coming back. The difficulty of encryption pushed many applications into HTTPS so they could stay safe, even though HTTPS isn't a perfect fit for every app.
With QUIC saying "You're as safe as possible and you have basically a UDP and TCP portal to the server, have fun", I think we'll see some custom protocols built / rebuilt on QUIC that were lying dormant since the age when encryption was optional.
For instance, multiplayer games could probably just use QUIC as-is. Send the real-time data over the datagrams, and send the chat messages and important game state over the streams. Instead of some custom game communications library, and instead of connecting TCP and UDP to the same server, one QUIC library and one QUIC connection. Now it's within the reach of a solo indie developer who wants to focus on their game-specific netcode, and not on re-inventing networking ideas.