Architecture and 3D graphics
Architecture is at the cross road between Art and Technology. In some way,architects are the inventors of 3D graphics. Think of the Renaissance in Italy during the Quattrocento when architects where also painters and discovered the perspective - Alberti for instance -
3D graphics is everywhere
Today, basic 3d graphic cards can handle millions of polygons. 3D has become mainstream. With free software like Blender, professional 3D work is open for everyone, and frequently with the most advanced technologies.
3D is the core of architects modern tool
Architects are now part of this world , 3D has become a tool you can't avoid any more. It is used in every studio, and has became very important for dealing with fast processes and the need to visualize the projects. I've been told that Jean Nouvel is very close to his in house 3D artists.
There is no architecture oriented open/free software
For some reasons,3d studio max is mainly used in architect's studios. Today, google Sketchup is getting well known and is good tool for architects. But it has limitations. It's not open source. It's not running on Linux.
Blender as a sketching tool
Blender can become a major tool in the field of architecture. But let be clear. It's not intended to become a CAD tool.Blender is for making images, animations, games. When dealing with large plans and constructions details, the architect need a very specific tool, witch Blender is not. This is the goal of FreeCad.
But this is not a limitation. Blender is open source, so people really interested with very specific task can make plugins or even branches of blender. Just have a look at how some scientists have hacked blender : connections with HD scanners, neurons and molecule modeling, robotic, and so on...