I think it'll happen incrementally, but also quite quickly once the ball starts rolling.
There will be already is a huge collective will to get past this current situation.
There is also a pressing, and growing, economic need to restart and re-stimulate many sectors of the economy. Claiming Brexit as any kind of success relies on economic activity within the UK.
The narrative from the government, and the media, will change. When we stop seeing ticker tape counts of cases, deaths and hospitalisations on the front pages daily. The government will start talking up how many people have been vaccinated -- even more than it is currently doing. The press will start running feel-good stories about how Connie and Ronnie in the Shady Pines care home have had their vaccines and can sit at a table, share a pot of tea and some cake, and play cribbage again.
We might also start seeing some credible data that demonstrates the relative ineffectiveness of more restrictive lockdowns (Stanford University has already done this -- there will be more.)
The people whose fear of going out is totally out of proportion to their personal risk will rapidly find themselves in the minority. So the social pressure will shift towards connected society again.
Some people will want to remain shut away, and will be able to adjust their own lives so that they do. Whether that means they miss out will be entirely a matter for them.
Others will have to tackle that fear and rejoin society as and when they feel able.
About 1,400 people die every day in the UK under normal conditions, roughly two thirds of these from either cancer or circulatory illnesses (heart attacks and strokes). We don't see a daily count of cancer or heart attack deaths in the press, even though these combined would be about 900 or 1,000 a day. Most people go through their lives without thinking about it too much or hand-wringing that 'something must be done'. (Which is not the same as not caring.)
Whatever you think of lockdown, I think we can all agree that it's not fun, healthy or a realistic long-term solution.