This week's Cabinet reshuffle will involve almost all 16 ministries, though not all the ministers are moving to new ministries, said Prime Minister Lee Hsien Loong.
Some key ministers will have their portfolios adjusted, but will stay on in places "where they still need time to continue to develop initiatives which they have started", said PM Lee on Friday when asked about the scale of the reshuffle.
He had earlier signalled there would be significant changes to the Cabinet before Parliament opens on May 7 after a month-long recess, to give younger ministers more exposure and responsibilities.
Analysts and Singaporeans have been watching for signs to see which office-holders will be moved or promoted.
The announcement of the Cabinet reshuffle will come this week, "so it is just a few days of suspense", said PM Lee in an interview with the Singapore media to wrap up his visit to London for the two-day Commonwealth Heads of Government Meeting.
The Straits Times has reported that three veteran ministers, Trade and Industry (Trade) Minister Lim Hng Kiang, 64; Manpower Minister Lim Swee Say, 63; and Communications and Information Minister Yaacob Ibrahim, 62, are expected to step down.
(For) some of the key ministers, their portfolios will be adjusted, but (they will be) basically staying in places where they still need time to continue to develop initiatives which they have started.
PM LEE HSIEN LOONG
On whether the reshuffle will shed light on who the next prime minister will be, PM Lee said leadership succession is a "continuing process" that takes time.
The younger ministers are working together on the Government's agenda for the President's Address and on tackling problems, he said, adding: "I am quite confident that gradually they are beginning to have a sense of one another and who they would like to have to lead them."
PM Lee also said he has given the younger ministers advice on crafting the Address, and they are now on the 20th draft of the speech that will be delivered by President Halimah Yacob on May 7.
"I have been doing these drafts for 30-odd years now and this is the one in which my drafting is the least of all," he said.
"Because the younger ministers have put a lot more effort in it and it will show."
Asked about PM Lee's remarks, Singapore Management University law don Eugene Tan said he could be trying to pre-empt any speculation or comments that may arise when a minister is not given a new assignment in the reshuffle.
Staying on in a ministry could be a better test of a minister's capability, and not being moved does not mean a minister has been ruled out of being the next prime minister, he said.
Being on the same portfolio for some time could mean a minister would be "strongly associated with that policy's success too, and would have a deeper understanding of that portfolio", added Prof Tan, a former Nominated MP.
He said PM Lee's comments could mean Finance Minister Heng Swee Keat would remain in his current role to carry out long-term fiscal policies, while Education Minister (Higher Education and Skills) Ong Ye Kung would continue with his portfolio to work on SkillsFuture.
The two men, along with labour chief Chan Chun Sing, are regarded as front runners to be the next prime minister.
Mr Heng had said in the past week that he would be happy to continue in his role.
Political watcher Mustafa Izzuddin from the ISEAS - Yusof Ishak Institute said all the current senior ministers of state could see a shuffling of their portfolios to give them more exposure, "though promotions to full ministers may not happen as there are limited spots".