Shabazz needs minutes, and for now its too costly for the Heat to give him minutes to develop. This to me is not a demotion, but a means to expedite his development. He'll get the 20+ minutes a night as opposed to the diminishing minutes Spoelstra's been giving him.
I saw a game recently and the Heat were struggling, Spoelstra didn't look his way when I thought Bazz could help. I also sensed something was going to happen to him then.
Spoelstra likes him, so I think its an investment decision, especially if they need him late season. He'll be a better player at that point.