I think the private pension becoming mandatory was a way to move away from state pension. In future (I dont know when but you can guarantee the government at the time will fuck it all up) there will be no state pension, that money will be redirected, because theres no way we will pay less tax.
And everyone "should" have a private pension.
Plenty of people will be in pension poverty, but I'm certain the government of the day wont care, or you'll get minimum top up benefits.
As for OP it's a good question, I think more automation of jobs, so fewer jobs, more working from home. Wages will increase soon, no one will be better off.
Housing stock, well a lot isnt suitable for current day living, so itll either be knocked down and rebuilt or revamped inside.
Healthcare spending will skyrocket. As others have said, obesity and related. And mental health, we cannot keep ignoring mental health issues.
I think schools will be built bigger, and a bigger catchment area, there are savings to be made in scaling up school buildings. I'm not a fan of this btw.
Self driving cars will be normal, public transport might actually get joined up.
Flights will be a thing only very very wealthy people can have. And we will be super pissed off about it, because they rant on about climate change to the many who can't afford to fly, but then they fly every week.
Smokers will die out, but the vaping scandal is just 20 years away.
Children the world over will no longer be exploited as cheap labour in mines and factories, this is of course pie in the sky thinking.
I think even with mass immigration there will still be fewer people in the UK, so the current monetary system will have to change. But what to, I dont know. Hopefully a fairer system whatever that looks like.