I don’t know about it not being replaceable. I did hear that they’ve upped the size of the battery so that it’s a really beefed up now (plus the screen was made into a glass screen, instead of plastic).
I guess we’ll see what the comments are about the battery, as soon as it comes out.
I don't know what the deal will be with the iPhone, but with the iPod if the battery fails under warranty they will replace it free. If it fails outside of warranty it's easy to get an inexpensive kit to replace it yourself. Doing that invalidates the warranty, but then it's already expired anyway.