Replacing TCP in the DC is a lot easier now with the advent of smartnic/DPUs.

You can make the server think they are using a perfect TCP connection even if the protocol is different. And the opposite, the server/app can use a new protocol like json-stream-whatever and the smartnic can proxy it onto a TCP session.

It turns out that cheap single purpose NICs were great for standardizing on thr lowest common denominator (tcp/udp) but now that it’s clear that the network protocol is the bottleneck, we can imagine and implement new protocols while maintaining backward compatibility.