Not necessarily. Yes, under Salic Law Henry should become king of Aragon. But the problem is that the Aragonese never really followed Salic Law, otherwise Henry should have become king of Aragon when Ferdinand II died. Instead, the king forced the nobility to accept his daugther Joanna and his grandson Charles as his heirs.
So, assuming that Juana Enriquez is barren (kill her earlier wouldn't help, the king would only remarry again) then you have three options: a) the king makes his daugther Eleanor of Navarre his heir, and so Aragon and Navarre are united under the House of Foix; b) the nobles force the king to accept Salic Law and Henry, Duke of Segorbe, becomes king; c) Ferdinand I of Naples, bastard son of Alfonso V (eldest brother of John II) decides to raise a claim to Aragon.
Also, don't forget that if Juana fails to give the king a son then his relationship with his eldest son, Charles of Vianna, might be completely changed. The odds of Charles dieing the way he did IOTL would be much smaller here.