No information confirms this, but if he's gone, the questions would be asked, "how or by whom"?
I could go over a few scenarios, but certainly one could be that he was getting closer to S Korea and maybe even the U.S and China or others saw a vital controlled satellite at their border disappearing. Could it be someone from the inside who wanted power? Maybe an enemy state who was concerned about the whispers lately he was considering a nuclear test (another reason China may have been responsible if they felt he was disobeying)?
Nobody knows anything right now, he could be inside watching MSNBC and being fed candy. However, if he is gone, even as he didn't seem very healthy and I even recall Tucker Carlson mentioning that he could hear Kim breathing heavily when he was nearby just while performing that short walk, I'd still be suspicious. When and if such tyrants fall, there must always be questions that are answered.