As someone that has used microsoft word, open office (when the #%^@ is 3.3 coming out? RC8! are you kidding me!), word perfect and even the ancient electric pencil I don't think kindle could realistically be used for word processing. Maybe another five years down the line.
You would need a touch screen or a mouse to really move the cursor around..otherwise functions would be slower.
Then again if they can take cd roms and have them work in conjunction with an Atari 2600..
there's a difference between possible and probable.