Absolutely zero chance of reducing our population.
First of all, we’re only at the start of the migration crisis. Last year, net migration was 600,000. That’s more than the population of Manchester. Africa has the highest birth rate in the world. In fact, the African population is set to double. I believe African women have five children, on average. In some countries the average is seven! Even if we managed to halve the numbers coming in, that’s still more than a quarter of a million extra people each year.
Second, radical life extension is going to transform society. Right now, serious people are working on life-extending drugs (Google senolytics, for example), and lifespans of 120, or even 130, could soon be the norm. This isn’t wacky sci fi. It’s really coming. Billions are being poured into research. David Sinclair, a professor at Harvard, recently said lifespans of 150 could soon be common. In other words, people won’t be dying and making room.
I have a horrible feeling that if humanity doesn’t reduce its numbers, nature will do it for us.