Modelling seen by the Government suggests cases could peak before falling sharply in the winter months - without having to introduce Plan B restrictions such as compulsory face masks, vaccine passports and working from home.
It is understood ministers have seen forecasts by several groups, with cases dropping to around 5,000 a day before Christmas in one scenario, the Daily Telegraph reports.
Professor John Edmunds, of the London School of Hygiene and Tropical Medicine and a member of Sage, said: "When we were doing the work about two weeks ago, the Health Secretary had made it very clear that the government was not planning to introduce Plan B in the near future.
“Our model was projecting that cases would start to decline some time in the autumn.
“However, the model also suggests that cases may start to climb again in the spring, due to a combination of waning immunity and increased contacts.”
Other experts say case numbers are being driven by children returning to school after the summer holidays, but increasing immunity through both infection and vaccinations could see this wane.
The October half term, which for many schools begins on Monday, is also expected to help bring down case numbers.
Meanwhile, ministers have doubled-down on their messaging that Plan B is not currently on the cards.
Health Secretary Sajid Javid told Sky News on Monday: "At the moment we don’t think the data shows that we need to move to Plan B but that said, it’s really important that we all keep playing our part.
"That means getting vaccinated, especially if you’re eligible for the booster jab please come forward, and also just being cautious on a daily basis and following the advice.”
On Sunday, Chancellor Rishi Sunak told BBC One's The Andrew Marr Show that the "data does not suggest that we should be immediately moving to Plan B".
The Government is coming under increasing pressure to implement Plan B after daily cases rose beyond 50,000 last week, while hospital admissions increased to more than 1,000.
Meanwhile Professor Peter Openshaw, a member of the New and Emerging Respiratory Virus Threats Advisory Group, said the current situation was "unacceptable".
He said: "I don’t think it’s a binary go for Plan B or nothing, it’s very clear that the measures that are in included in Plan B are sensible and not very disruptive.
"It’s not problematic to give clear leadership about the use of face masks, and working at home if you can is also not particularly disruptive for many people.
“Those measures are likely to lead to a pretty good reduction in the really unacceptable number of cases that we’ve got at the moment.
“What we’re facing at the moment is unacceptable we’ve got roughly 1 in 55 people infected, which is an astonishingly high rate compared to most other west European countries.
“This is connected with the lack of clear messaging about sensible measures that we should all be taking in order to reduce the spread of infection.”
The UK recorded 39,962 coronavirus cases on Sunday, and a further 72 deaths within 28 days of a positive test.