It will never be automatic process. The structure of the model is totally different. For example there are no layers in Revit and There are no Worksets in Archicad.
You can export 3D information via IFC, but it's not all roses as again Revit and Archicad have different tolls for different things. For example no slanted walls in Revit, no parts in Archicad.
You can import 2D data via dwg.