:I believe that if we've made it to the 29th century without bombing
: each other to the Stone Age or making our planet unlivable from
: environmental disasters, it will be a good place to
: be, with a good balance.
Those are pretty big ifs. Some years back, I read a book called The Third Millenium, but I can't remember the author and searching for it yields a lot of unrelated religious stuff. The book was written from an historical perspective, and confirms a lot of what you suggest (although Earth's capitol city ends up being on Antarctica, which is neutral turf).
The environmental issues are not inconsequential (as they weren't in the book). Global warming is almowst certain at this point no matter what we do - it is now a matter of degree. All of those wonderful costal cities you mentioned will be partly under water!