It depends on what you mean by model.
If you mean Swing model eg TableModel, then although a complex GUI may warrant separate packages, it is equally arguable that they can all go in the same package. As regards is M, V or C GUI or not, then with this definiation of model, yes they most certainly are all GUI. Although a Swing Model class could be used for another kind of view, it would be a bad idea.
On the other hand, if you mean by model, the business model. Then yes that should be in a different package. The only big question is do you put htat package server side or client side?
Which neatly segues into a discussion about thin vs thick clients