the one guy id sell is Higuain actually. he wont have a long career imo, can get you more money, and would open up the CF role for Dybala to take. Mandzukic has the athleticism, the size, strength and stamina to be a useful player even when hes 35, on limited playing time.
if you need money for a WC player and Mandzukic is the only one that can get you some, then sure, in 1-2 years im OK with him leaving. right now, especially when hes still a key performer, a clear no from me.