Do you need to worry about this?
1. You have more than one model in your layer (Apart from the base layer i.e. ISV layer)
2. The elements in your project can belong to more that one model in the same layer.
If you answered yes to any one of them, then word of caution, do not move the project directly.
Moving a project to another Model is a different Cookie. IT MOVES ALL THE ELEMENTS INSIDE IT TO THE LAYER YOU MOVE THE PROJECT TO!!! Yes that is in CAPS.
Method 1: Create a new Project in the desired Model and then Drag the elements from the original project into this new one.
Method 2: Database Crazy: You can play with the model database to do this, but i shall hold my guns on this one. I wouldn’t recommend this right now. Hint: ModelElementData.ModelId
Update 16/04/2015: I have created a script to assist you with this. Use this carefully. Link: https://github.com/shashisadasivan/MyScripts/blob/master/AX%202012/SQL/MoveProjectToAnotherModel.sql