Sometimes you never know.
Though never diagnosed with anxiety, DS was always very clingy and always wanted to know that a parent (preferably both) were in sight. Even if I went upstairs (telling him I was going), he would call for me panicked. Though this has subsided substantially as he has gotten older (he's 10 and normal at school, etc), I will still occasionally see him check to see where I am.
I took him to
Disneyland regularly since he was one year old, just the two of us. He wanted nothing to do with costumed characters of any kind, nor would he go on any dark rides. He was a daredevil as long as the ride was outside.
Flash forward to when he was five (or whatever the minimum age for Jedi Training is) and he decides he wants to do this. I'm thinking that we will try it but he will never go through with it.
Flash forward again and he is selected from the crowd (they used to do it that way and thank you to the mom who took him from our second row position and stuck him out in front with her kids!).
Imagine my surprise as the kid marched out there never looking back, and did the whole thing. The kid too terrified to take a picture with Mickey or even a princess had no problem fighting a scary villain. Desire won over anxiety.
As the others said, watch the videos. He might even be able to learn and practice the sequence. Let him know whatever he decides (regardless of when he decides it), you're ok with his decision. Show him where you will be and wait to see what happens. You might be surprised or at least certainly proud that he stepped out of his comfort zone.
...and seriously, I still owe that mom, who pulled DS up front, a case of wine.