Comment by toast0

If someone with leverage (probably Apple) was willing to put the effort to push it, we could have TCP Fast Open, and you wouldn't need an extra round trip for TCP+TLS. But also note, TLS 1.3 (and TLS 1.2 FalseStart) only add one round trip ontop of TCP; going down from 2 round trips to 1 is nice, but sometimes the QUIC sales sheets claim 3 to 1; if you can deploy QUIC, you can deploy 2 handshake tcp+tls.

Apple put in effort to get MPTCP accepted in cellular networks (where they have direct leverage) and having it out there (used by Siri) puts pressure on other networks too. If they did the same thing for Fast Open (SYN with data), it could be big.

Unfortunately, I'm not sure anyone other than Apple is capable of doing it. Nobody else really has leverage against enough carriers to demand they make new TCP patterns work; and not many organizations would want to try adding something to SYNs that might fail. (Also, MPTCP allows session movement, so a new TLS handshake isn't required)