They don't NEED to, that's just your opinion. Much of this depends on the next contracts, and the salary cap. The Salary cap should be $92 million in 25/26, If you assume we keep all four, on new contracts... what's that look like Matthews $13 mil, Marner $12 mil, Nylander $9 mil, Tavares $5 mil? That's the same total dollars as today.. but with an extra nearly $10 mil on a better supporting cast.
If the right deal came along though... of course you look at it. If Keller demanded out of Arizona, and you could pick up Keller and McBain for Marner... sure... you open up all kinds of cap, and don't lose much in quality. You also pick up a guy who will be that physical type, good defensively, cost controlled for a 3C too.
But forcing a trade.. we are going to lose, and the team will be worse for it. You wait for opportunity.
If Calgary wants to keep Lindholm and Hanifin, maybe they consider moving Weegar... Weegar was a Treliving contract.. Weegar would be a guy who would upgrade the second pairing, solid guy when he's not THE guy.
This premise that WE MUST move out one of the four is false though.