I do not like the character Wilmer Valderrama plays and never will!
I think Gibbs should leave he looks tired. I would like him to do a show three to four times a year in a advice role only.
I think Dietzen, Sean Murray and Rocky Carroll should stay and gradually leave after the new characters have been been introduced a year or two. I think there should be a couple of characters from the beginning years. Totally change the main characters is like it's a new show. I do not like the new team leader. He looks old and gray and boring. Get someone younger, and more attractive under 50. The grey looks like he may not be there long on the show, in other words retire also like Gibbs.
FYI, I did not like ncis New Orleans location and team seemed to change a lot?. The team leader is okay on ncis New Orleans, it took me time to like him. I would not go out of my way to watch it.
Gibbs, new Gibbs. New Orleans all have grey except Hawaii. (not sure about LA). A Tony aged person person. I only watch NCIS none of the others except occasionally when bored.
Law & Order SVU still has several original characters, not main characters changed.
I have grey hair, I am 73..