The retail giant made the prediction in its latest Future of Food Report, which looks at the changing landscape of consumer habits, and predicts how people may eat by 2025, 2050, and 2169.
It said an 'unprecedented awareness of animal welfare, health concerns and eco-anxiety' means people could put the planet first when choosing their food.
Vegan and vegetarian
"As the global trend for meat consumption increases, Britons are changing their diets to eating less meat," the report says. "Today, flexitarians, who are those actively reducing their meat consumption, make up a fifth of Britons, while vegetarians account for an eighth of the national population.
"Vegans, those who eat no meat, eggs or animal products, are still in the minority at around 600,000 in the UK. However, with the rise of an ecologically aware new generation, driven by health concerns
and environmental determination, vegetarians (including vegans) look set to make up a quarter of British people in 2025, and flexitarians just
under half of all UK consumers."
Sainsbury's vegan and vegetarian sales
In mid-2018, Sainsbury's revealed that sales of its meat-free range were growing significantly weekly - leading the outlet to expand its animal-free offering.
James Hamilton, Meat-Free and Ready Meals Buyer at Sainsbury's, said: "We are seeing an increasing interest from our customers in plant-based foods, with sales of our current meat-free range growing 20 percent each week. We're always exploring new ways to offer even greater choice, quality and value."