It is Apple's practice to establish a price schedule and keep it in all subsequent model. There are circumstances where this changes, but more often the price goes lower. The standard rumor that is consistent is that the iPad 2 will be kept as a low end entry model, probably at $399, maybe lower. It makes more sense than an 8" model.
im pretty confident the iPad 3 wont start at launch with a more expensive model, first of all, they would have to make all 3 sizes more expensive, and it doesn't really seem logical. i think if every online rumor about the ipad 3 is 100% real, and they unveil some awesome machine that surpasses everybody's expectation, then yeah maybe it'll be more expensive, but that's highly unlikely to happen. the other thing that makes me think we'll see the same price plan for iPad 3, is if you take a look at the video of steve jobbs unveiling the iPad 2, when he's talking about the price, he seems very excited to let people know that it will be launching at the same price plan as the ipad 2, then states the first generation ipad will be discounted. but i really felt that it was included in apples ethic not to start off new models 200-250 dollars more expensive than the previous model. and i think that's great, and a smart way to inshore sales.