Based on him being one of the most coveted defenders in the game. Us, City, Barca, and Lyon were all sniffing around, and he'll definitely be moving on next summer. Based on him having those attributes on the ball, but also being much better in the air than Lindelof, much more assertive in the tackle, and also is a mainstay in one of the best international teams in the world.
Benfica have no need to sell Ruben this season, after the amount of money they've made in the last 24 months, so his new contract suits both sides, but he will move on and he will be a world class defender. Really not sure why you'd bother arguing that.