Changes to the Cabinet to put younger ministers in key posts will be announced some time after the Budget debate next year.
Prime Minister Lee Hsien Loong indicated this timeframe for a reshuffle in an interview with Singapore media last Saturday in Argentina, where he was attending the Group of 20 leaders' summit.
The Budget debate ends in March, and PM Lee hinted the changes could be made in April or May.
But for the leadership transition to the fourth-generation (4G) team to go according to plan, the People's Action Party (PAP) must first win the next general election, PM Lee added.
"It depends on the party staying together and the party winning elections. And the first thing to do will be to win the next election," he said.
Finance Minister Heng Swee Keat is expected to be deputy prime minister, the post which the second and third PMs - Mr Goh Chok Tong and Mr Lee - held while they were earmarked for the top post.
Mr Heng, 57, was announced by the PAP as its first assistant secretary-general on Nov 23 following internal party elections, making him the most likely candidate for future PM, while Trade and Industry Minister Chan Chun Sing, 49, was named its second assistant secretary-general and Mr Heng's deputy.
Asked if Mr Heng would be the country's fourth prime minister, PM Lee replied that the PAP had made it clear that Mr Heng would be its next leader.
ON THE NEXT GENERAL ELECTION
I will lead the party into the election. But the content of the policies and how they are presented, and what they want to do... the young ministers will have a lot to say.
PRIME MINISTER LEE HSIEN LOONG
"The 4G ministers have decided that Swee Keat will be their leader... and the MPs have endorsed this conclusion. The party's position is clear."
But he added: "First, we have to fight an election, we have to win the election and after that if all goes according to plan, well the succession happens within the PAP, there are no surprises."
PM Lee said this mechanism for leadership transition had worked out well for Singapore in the past, by providing stability, continuity and renewal of leadership and policies.
PM Lee, 66, had previously said he hoped to hand over the post of PM to his successor by the time he turns 70 in 2022. The next election must be called by January 2021.
Asked if he would appoint Mr Heng as a DPM at the upcoming reshuffle, PM Lee replied: "In due course I will reshuffle Cabinet, then you will see what we do."
The last reshuffle was announced in late April this year, and PM Lee added: "So next year around the same time, I think it is reasonable."
PM Lee also gave a flavour of how the fourth generation of leaders would take the lead in the coming election. They will do so by setting the party's agenda, working out its policies, preparing the manifesto, making the pitch to the public, actively campaigning and organising the election, he said.
"The 4G will be very much in the thick of things. Even in the last election, they were very actively involved in organising although... I was more prominently making the pitch," he said.
"I'm still the leader, so in the next election, I will be the leader and I will lead the party into the election. But the content of the policies and how they are presented, and what they want to do, I think the young ministers will have a lot to say about that," he added.
PM Lee also said the PAP would be going into the next election with a team that has "depth" - comprising not just the PAP's present leaders who are in their late 50s and early 60s, but also "the next generation of leaders in their 40s and 50s, ready to take over".
"That's a very strong message, which goes beyond any specific policies and manifesto items or promises," he said. "The commitment is we are here to serve and not just for now, but to serve into the future and you can rely on us."
Mr Heng said the 4G ministers will launch a series of discussions with different groups of Singaporeans after the Budget.
These will build on the Our Singapore Conversation feedback drive he led in 2013, he added. "We want to have some time to look at what are some of the fundamental, long-term issues that as a country, as a society, we need to address."
SEE TOP OF THE NEWS: 4G ministers will start discussions with S'poreans next year: Heng