Defending champions Jamaica, without the rested Usain Bolt, advanced with a blistering time as did the United States, to set up another mouth-watering showdown when Bolt will return hoping to complete his "double-treble" having bagged the 100m and 200m.
The United States, anchored by 100m bronze medallist Justin Gatlin, won their semi in 37.38 and Jamaica, with 100 and 200 runner-up Yohan Blake running the third leg took theirs in 37.39, the third and fourth-fastest times ever recorded.
Both squads have fresh blood to bring in as the U.S. did not risk Tyson Gay or Ryan Bailey, their two best performers in the 100m and still posted an American national record.
"The past couple of years we defeated ourselves," American second leg Darvis Patten told reporters.
"To surpass people like Carl Lewis, Dennis Mitchell, Leroy Burrell and Andre Cason ... to be in the same category is unbelievable."
Blake was similarly upbeat.
"We have guys running fast and without Usain we still ran a fast time," he said. "I think it (the final) is going to be interesting. The Jamaican order will be the same with Bolt substituting Kemar Bailey-Cole as the anchor."
Canada, Japan, Trinidad and Tobago and France are likely to be fighting out for the bronze - a medal the host nation would have had in their sights after finishing not far behind the Jamaicans in what would have been a sharp 37.93.
However, while the crowd were celebrating, the British athletes were gathering around a TV monitor looking worried as the examined the final changeover between 21-year-old Dan Talbot and 18-year-old anchor leg Adam Gemili.
It was immediately obvious that they had not only strayed beyond the allocated changeover box but that Gemili had also run out of his lane and the disqualification came soon after.
"I don't know what happened. He just seemed to get out very quickly and I couldn't catch him," Talbot said. "I'm really gutted and it's devastating."
Lead runner Christian Malcolm said: "It's one of those things that happens but it's a fantastic performance to run the time we did. Daniel has come in at the last moment. This is a big stadium and it can be overwhelming."
Britain's women did make it safely through their 4x400m relay semi, finishing third in their heat. That semi was won by the United States, with Russia second and the Czech Republic qualifying in fourth.
Jamaica won the other heat, with Nigeria, France and Ukraine following them into the final.