I know several who bought in Brixton in the late 60's and paid £800 for a 4 storey town house etc...sold up for 2m and went back to Barbados etc!!
But they couldn't have made £800k without the gentrification that drove up prices.
And that gentrification probably also left their children unable to buy in the area.
I think individuals selling at opportunistically high prices is something that happens in coastal / holiday areas, too. And people moving out of a city to a retirement place near the sea, and releasing capital.
But individuals making one-off bonuses from rising prices doesn't drive gentrification and the benefit to those individuals doesn't offset the effect on the area and communigty as a whole.
I agree, no area 'belongs' to any one group of people, but Gentrification happens in areas that were in the past the only places the poor could live and build a community, and now those communities are rent asunder. Gentrification is usually driven by some council - developer partnership which in theory is to 'regnenerate' for the benefit of all, with jobs and leisure centres for the community. But the commercial partners always start reneging on the social housing, bringing in chains, putting up rents...and so it takes root. And before you know it, you have a Heygate situation.
Guinness Loughborough Park Estate and Myatts Fields in Brixton, now The Oval Quarter and Electric Quarter or some such nonsense. At astronomical prices.
Prices have risen all over London, and in may places all over the country - but rising prices in Kensington are not the same as gentrification.