I voted two years, with the hunch that we win a NC next year. But I see a conventional refrain that a player will leave as soon as the money or prestige of being a high lottery pick enables that. That is not a given.
Tim Duncan played all four years despite being ready and destined to be rewarded quite well for leaving early. He also was a player of high character. There is research to link the two.
Nothing in the archives of brain health research links money and prestige to better brain health. People leave early because of cultural expectations and ambitions that have been cultivated, not due to natural health factors. However, there are links between brain health and longevity to things like social bonds, self-improvement and the sense of purpose behind the rewarding pursuit of a goal.
These are some of the health factors that lead a person like Tim Duncan to stay in college all four years, and may lead to DC staying for at least two.