With the Freeze Drawings extension, you can separate a view from your object model so that the current state of the view stays unchanged ( or frozen). The extension was developed using the DWG Import and DWG Export mechanisms in Autodesk® Revit®.
You can freeze the Current View or Selected Views and all frozen views are preserve a point in time of your project, these views are no longer part of the model but are placed in a Drafting view.
You can also have the option to export the views to a DWG file with options to control the DWG output.
Update Nov 2015: 2015 add in does allow you to freeze 3D views but not sheets.