I believe (and I hope I am right, because it is my greatest dream), that the future of architects and designers will be to use a pen on a computer screen.
in my opinion the fusion of handdrawing and computer aided design is the only sensible solution.
the simple reason for that - try to write your name with a mouse... you will barely succeed in producing clean hand writing. you are simply much more precise with a pen than with a mouse.
of course technology has to improve before that truely works. but it is not too far in the future anymore (I hope
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even today there exist prototypes of so called e-paper that are as thin as a fraction of a millimeter and are equal to newspapers in terms of contrast (because they really behave like ink on paper, reflecting light instead of emmiting it).
at the moment these displays are restricted in size to some inches. but the near future they will be available in A3 size with a resolution high enough to give a true, pixelfree image, even when looking at it upclose.
I imagine using your hands (similar to the iPhone) to navigate across your canvas. you can choose to stick the drawing stage to your screen to imitate the behavour of real paper. but if you run out of space you can simply unlock it and move it arround.
the touchscreen will destinguish between hand- and pen-input. that enables you for example to rest your and on the screen when drawing with the pen. drumming with 4 fingers of one hand on the screen in a short succession calles up a context menue. otherwise the screen stays completely free of any buttons (except of a colour pallete perhaps).
the tip of the pen will be a high-tech device on it's own, not only measuring the precise pressure and angle of the pen, but also changing it's smoothness (through a material that changes it's attributes when recieving an electric current). thus the pen can simulate different types of pens (like pencil, marker, brush) and give the impression of drawing on rough canvas (instead of completely clean plastic).
you start your design with an interface, that is close to Photoshop. you sketch like with a real pencil. but you have the advantages of a computer - you can change your pen without laying your drawing device out of your hand, you can change colours by tipping it on a button on the screen. most important you have a "undo" function. you can draw in layers easily, fill faces with colour, draw only in a selection - everything a piece of software can provide.
in addition to that you may have aids to slightly correct your lines to a coordinate system when active or to help you drawing a precise circle, ellipse, rectangle...
when you finished your first sketch, you can use the SketchUp tools, push/pull in the first place, to advance into 3D - within the same application. this new SketchUp will refer to faces rather than to edges (because you draw lots of small lines, when sketching). you can define the grade of simplification (like ignoring small lines, closing gaps) and angle-/shape-correction (putting lines to a right angle, where obviously intended, translating sketched curves to arcs, circles, bezier-curves), even choose different correction values for different parts of the same drawing.
if you need a break, you will just leave your sketching tablet lying on the table. the drawing will still be visible, because an e-paper display doesn't need engergy to display information (only for changing it).
you can easily transfer sketches/models from your tablet to the large table-display, simply by performing a dragging movement starting on the tablet display (lying on the table) and ending on the table-display. because it is one continuous motion (same speed, finger tip size and curve) the two systems will automatically synchronize the data.
then I poste one drawing by simply dragging it into one of the SCF gallery threads. one of you guys sketches some suggestions on a new layer and posts it back in the thread (only the layer with coordinate information, which I then drag onto my drawing...)
sorry guys, got carried away way too far 
could go on for hours.
essence of what I wanted to say: the natural and intuitiv use of a pen will be combined with the precision and multifunctionality of a computer - in sketching, as well as in construction drawing.