While this is true, if we put him alongside Pogacar, he doesn't actually have that much time on his side. The age difference between them is only 16 months - Pogacar really isn't that much older. I often forget, because Pogacar has been riding the Tour de France (and winning it) for so long that it makes me think there is more of an age difference between him and Evenepoel than there actually is. To be honest, they are close enough in age that it is not definite that Pogacar will be the first to decline. But the biggest issue for Evenepoel, I think, are the younger riders coming up, who could well start to challenge him just as Pogacar takes a step back.
Anyway, all that really means is I agree that he should be riding the Giro or Vuelta as well as the Tour, especially if there is a chance to avoid Pogacar and Vingegaard. Next year could be tricky, if Vingegaard rides the Giro and Pogacar finally takes on the Vuelta. But a rider of Evenepoel's calibre certainly shouldn't be waiting around for Pogacar to decline.