There have been a lot of tiles seen on marketing material (ahem, angry birds) and there are more apps being worked on than are currently out. Unless Amazon is planning to go out of business in the next few weeks, they'd be insane to not put an Amazon app out.. so yes, plan on one. When? Any Amazon employees on here?
I am guessing we will see Amazon and Kindle apps sooner than later. I am quite excited for the Amazon app, use it alot of my BB anyways. With Microsoft and Amazon being almost next door, I think they are hard at work on this together. =)