#2. He isn't - WWE acknowledging his departure in storyline
If you noticed, soon after the announcement of his departure from WWE was made, there was instant curiosity as to whether it would be acknowledged on WWE television. During his brief two-week TV feud with EC3, there was no acknowledgement whatsoever that he was leaving.
In fact, it was only after Roman Reigns returned that they began to acknowledge it. Reigns had mentioned that he had "no idea" what Ambrose's future was, while Renee Young said that he was moving on to "greener pastures".
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Normally, WWE wouldn't acknowledge this in storyline unless they really wanted fans to believe that he's leaving, only for him to end up staying. It's a very classic move by WWE, and it's understandable as to why many fans took this as an indication that he has, inf act, re-signed with WWE. That's something we'll only know later.