Raila Odinga and Kalonzo Musyoka will be sworn in before the end of January, the People's Assembly organising committee has said.
The committee chaired by economist and NASA strategies David Ndii said the Assumption of Office team was fine-tuning the oath-taking roadmap.
"The swearing in of the NASA leader is well on course and the Assumption committee, to be named soon, will announce the exact details," he told a press conference in Nairobi on Thursday.
Coalition principals Raila (ODM), Kalonzo Musyoka (Wiper), Moses Wetang'ula (Ford Kenya) and Musalia Mudavadi (ANC) are expected to name the members.
Ndii, who is the brains behind the People's Assembly concept, noted power does not lie in instruments but with the people.
"What power do you have if people turned their back on you at Kasarani stadium?" he said when asked if Raila would take instruments of power at the ceremony.
"The country we have now is not working. We must reconstitute Kenya afresh."
President Uhuru Kenyatta and DP William Ruto were sworn in at the stadium in Nairobi on November 28, a ceremony that cost Sh300 million.
NASA has also lined a number of People's Assembly conventions this month. They will culminate in a major one in Nairobi where Raila and Kalonzo will be sworn in as leaders of the People's Republic of Kenya.
"It is going to be the biggest gathering since independence," Ndii said.
The Opposition will head to Kakamega county on Sunday for the second People's Assembly convention.
The first one was held at the Coast in December.
ODM executive director Oduor Ong'wen - also a member of the People's Assembly organising committee - said other regions will convene similar assemblies before end month.
He said their plan is for an inauguration and a broad process of entrenching electoral reforms.