probably, but you never know. At Lundkvist's age Fox was still playing college hockey so if he keeps developing at that rate he will be better than Fox. Also there were plenty of Elite looking players that suddenly declined.
It’s true you never know, but there’s zero reason for the Rangers to do anything unless A) Fox falls off a cliff, and/or B) Lundkvist matches his progress.
And if the latter happens, you damn well better believe that the Rangers would likely go completely out of their way to accommodate both in the lineup or pursue a center of equal value who can center the first line for the next 10 years.
But the odds say matching Fox is going to be a tall order and he’s gonna be their keystone on defense for a very, very long time.