More homes could eventually be built in sought-after areas such as Tanglin Road and Paterson Road in the city, with some rare sites earmarked for future residential use.
The most eye-catching are the former Ministry of Home Affairs Phoenix Park site in Tanglin Road, and the former Overseas Family School plot in Paterson Road, near Orchard Road.
These sites have been returned to the Government, or have been put to temporary alternative use.
Analysts say development sites in these swanky areas are very hard to come by and would excite developers. But they are not likely to be put on the market any time soon.
SLP International Property Consultants executive director Nicholas Mak said, "I don't think there's any hurry to sell the sites. It's probably going to be five to 10 years down the road. Land bidding is so hot, they would just be adding fuel to the fire."
Responding to a Straits Times (ST) query, the Singapore Land Authority and Urban Redevelopment Authority said the Overseas Family School site is available for short-term use. It is now unoccupied.
The site will be put up for interim use as a commercial office space before it is made available for future residential use, with commercial space on the ground floor, the authorities added.
Consultancy JLL estimates that 450 to 700 homes could be built on the 25F, Paterson Road site based on the two current plot ratio guidelines - 2.8 and 4.9 - for the location.
Its projection was based on the assumption that the commercial space occupies 5 per cent to 10 per cent of the gross floor area, and the average apartment size is 100 sq m.
The plot, which is behind the Thomson-East Coast MRT Line construction site, spans nearly 15,700 sq m and has a gross floor area of 10,678 sq m.
Another site identified for future residential use is Phoenix Park at 300 to 320, Tanglin Road - set in a sprawling precinct with a cluster of colonial-style buildings and lush greenery.
The authorities said the site is let out to LHN Facilities Management until August this year. The tenant has an option to renew until the end of 2020, although it is not yet clear if it will exercise the option.
Parts of the Phoenix Park site are currently occupied by the Avondale Grammar School and businesses such as Space Matrix Design Consultants and Boufe Boutique Cafe.
About 850 to 1,100 homes, with an average size of 800 sq ft to 1,000 sq ft, could be built on the Tanglin Road site based on the current plot ratio of 1.4, consultancy Colliers Singapore estimates.
However, analysts reckoned that the site may come with potential building conservation requirements or height restrictions given that it is near the Brunei High Commission.
Said Mr Ong Teck Hui, national director of research and consultancy at JLL, "(It) is likely to be developed as a low-rise condominium similar to the adjacent Tanglin Park. This will be in keeping with the low-rise and wooded character of the surrounding area."
The Tanglin Road site has a land area of nearly 59,629 sq m and a gross floor area of about 13,417 sq m.
Potential development sites could also emerge outside the city area, such as at the former sites of Bedok Town Secondary and Henderson Secondary.
The Ministry of Education (MOE) told ST that the two plots and another at the former Pioneer Secondary School at 21, Jurong West Street 81 were returned to the state recently.
A tender for the reuse of the Jurong West site was called last month, for it to be repurposed for foreign-system school use.
The uses for the other two vacated schools at 232, Bedok North Street 3 and 100, Henderson Road are still being reviewed, the authorities said.
Cushman & Wakefield research director Christine Li noted: "The former Henderson and Bedok Town secondary schools will be suitable for Housing Board flats, as the Government intends to introduce more flats in mature estates for buyers who wish to live closer to their parents."
Ms Li reckons the Henderson Road site could yield 900 units on an estimated plot ratio of 2.8, and 750 units on the Bedok plot based on an estimated 2.5 plot ratio.
The MOE said there are 14 to-be-vacated school sites occupying about 40ha of land. "MOE will assess the need to retain these sites - for example, to use them as holding sites for schools undergoing upgrading." Disused school sites will be returned to the state if the ministry has no plans for them.