I bet Naruto can tell if he's alive or not. He used sage mode a while back to notice that Kakashi was dead and again to find out that Hinata was still alive. He addressed Obito before Madara told him he's gone, so I think that might mean that Obito's alive just not conscious or in control. He also could have addressed him because he was in front of him. Anyways, I think Naruto would know. Now if only we could read his mind.
I want him to be alive because now that he has both sharingan we have to see his susanoo. It would be lame if we never got to see it.