IMHO, if it's not feasible today because of speed, bandwidth, ram, disk space...etc., you can bet it will be in the very near future. 
The beauty of WPF is that it will make many of today's hard tasks a snap.
This can be a recipe for disaster when some folks overuse it (The classic example still happening todate is powerpoints with black background, gold font color, lotsa images and cutom animated till the character level when the audience are executives looking for facts and numbers).
 However, this will also unleash the creative potential of so many others who know how to create great user experiences.

P.S. I'm not a flash developer but I guess the real value of WPF will not be as a competitor to photoshop, flash, Maya..etc. It will be in the ability to finally easilly integrate with the S/W being developed.