True--at the end of GFII. And, Tom replies: "Why do you hurt me, Michael--I've always been loyal to you." (Notice how the camera pans to Neri, smirking--he must have been the source of the info about Tom being offered a position outside the Family.)

After the Tahoe shooting, Michael tells Tom: "Right now, you're the only one I can completely trust." It's fair to note that Michael began that scene saying: "There's a lot I can't tell you about." You have to wonder: What couldn't he tell Tom about that Tom already didn't know, or couldn't infer? I think at that point Michael wasn't questioning Tom's loyalty ("You're gonna take over...you're gonna be the Don...I give you complete power over Rocco and Neri...over Fredo and his men..."); he probably was being Michael: tell Tom the minimum he needed in order to do the job Michael was giving him...temporarily.