BBC reports that Boris Johnson is expected to make the announcement of forwarding the date of the ban to 2035 later today (04/02/2020). This will happen at an event to launch a United Nations climate summit, COP26, in Glasgow in November. 

It is also reported that the ban on selling new petrol and diesel cars would come even earlier than 2035 if possible. Included in the ban are petrol, diesel and since 2017 also hybrid vehicles. This means that people will only be able to buy electric or hydrogen vehicles once the ban comes into effect. The Committee on Climate Change had recommended that the government brought forward the target to at latest 2035 and preferably to 2030. 

Read Transportation Professional's technical article from February 2020 "Understanding public attitudes towards electric vehicle use" here

Despite the rise in the number of licensed Ultra Low Emission Vehicles (ULEVs) on UK roads – 200,000 ULEVs were registered in Q4 2018 - ULEVs only represent 0.5% of the total number of cars licensed. According to the International Energy Agency’s 2017 EV outlook, these figures place the UK fourth worldwide by market share, and seventh by volume. Going forward, projections by National Grid suggest that the UK stock of EVs could reach between 2.7 and 10.6 million by 2030 and could rise as high as 36 million by 2040.

Source:  https://www.bbc.co.uk/, https://researchbriefings.parliament.uk