Yes, I know there are a few people who have said "He is fine, trust us", but it would take all of 2 seconds for him to send a message himself, a picture, a video clip, stand by the window, or go on the balcony, and there has now been a very long, uncharacteristic time window where he has not done this. He has many means of communication, regularly has visitors, and has a very legitimate reason for doing it (to silence all the people who are concerned, constantly Tweeting at them, calling to cease donations, etc.) - so the fact he hasn't is worthy of our suspicion.
EDIT - I really did mean "didn't want to start full discussion", because there apparently is a whole lot more circumstantial evidence, including regarding some of the people you mentioned (like some members of his legal team being barred entry), but seriously, I'm going to leave the fullness of that discussion for Reddit, and think anyone who is interested in it should take it up there.