You didn't include "build new facility" in your choices, so I didn't vote. I would vote no on expanding Cameron, but a new facility can be built and still preserve some of what's good about CIS.
The problem with building something bigger, as some folks have mentioned, is that there isn't a large population around to support large crowds consistently. There is the competition for relatively neutral potential customers with Chapel Hill nearby. Plus, Duke is one of the smaller ACC schools in undergraduate student population at 6,300.
Consider other ACC facilities:
It seems there is consensus that the Dean Dome is too big with its capacity of 21,750, despite a large undergraduate student population of over 23,000.
The Maryland Comcast Center was done right with a capacity of almost 18,000 and the student seats are near the floor:
"The student section contains 4000 seats arranged in the first ten rows on all sides of the arena, plus the most notable feature of the arena, the steeply pitched seating area at the west end of the arena behind the visiting team’s second half basket, informally known as “The Wall.” Originally designed to reduce excavation costs due to a hill, the area features 2600 student seats meant to intimidate opposing players who shoot free throws in the second half."
(Wikipedia)But the undergraduate population of U. Md. is 26,000 and D.C. is very nearby, so it is fairly easy to fill.
The new John Paul Jones Arena at U. Virginia seats 15,219 for basketball and features coaches' office complexes, locker rooms, a training room, a strength and conditioning area and an equipment room. However, again U.Va. undergraduate enrollment is double that of Duke's at 14,000. Plus, D.C. and the northern Virginia suburbs are just 2 hours drive away. I bought a 5 game series of seats this season. I do not know yet how they manage their students at the games.
Wake's Joel Memorial Coliseum seats 14,400 and is usually pretty full as I understand. I expect it will be this year since the team is pretty good. Wake, however, horribly mismanages the student seats. The "Screamin' Deacons" are boisterous but they are put in one corner and the numbers are limited to 2,250 out of a total undergraduate enrollment of 4,400. Skip Prosser did a great job of boosting student interest in the team, and of course having Chris Paul there helped quite a bit for a couple of years, too.
But Wake's example on size alone is encouraging for a new Duke facility. It wouldn't have to have all the auxiliary facilities such as practice gyms, with Duke's new practice facility in place. However, it could serve as a multi-function facility as many of the other larger arenas do, with concerts, university-wide gatherings, commencement in case of rain or unbearable heat, etc.
CIS is a shrine, of course, with many great memories. One of my own was the first time I set foot in it a little over 4 years ago last summer when I was taking my son around on college tours. The two of us got in when it was empty and we walked out on the floor, both of us awestruck as basketball fans. I think he decided at that moment Duke was the place for him.
But a new place would develop its own memories as time and seasons come and go. The Maryland Comcast arena should be the model for student seating. They are close to the court and surround it. The Crazies could still be loud and boisterous in that kind of configuration. That arena configuration has nothing to do with how obnoxious Maryland fans are, the worst in the ACC in my book.