Sure, but we're nowhere near the planet's maximal capacity, won't be for generations, if ever. By the time we're remotely near that, a Dyson sphere/ring could extend that for hundreds of generations more. The idea of maximal density may bring to mind dystopian sci-fi, but eg Judge Dredd's urbanized New England was less dense than Kowloon/Hong Kong is now. The demand curve, thus, is functionally infinite, same as the sun's lifespan. It'll expire after millions of years, but even my great grand children will be long gone by then, so the astrophysics of it mean that the statement "the sun will last forever" isn't literally true, but functionally, it is.