No. Currently a significant amount of latency in opening a web page is the DNS resolution (for half a dozen domains). TCP adds a lot of overhead compared to UDP.

But a case can be made that large requests should be TCP only.

> TCP adds a lot of overhead compared to UDP.

Not if you simply keep a TCP connection open and use SYN cookies on the servers. Many DNS servers already support TCP (though I'm pretty sure you need a new connection for every request).

That'd likely result in increased traffic and slowdowns even in normal cases.