Releasing the book after the announcement makes sense if there's a long wait between TES:V's announcement and its release. If there is a shortened period of time between the announcement and release (as Todd noted), then it may make more sense to announce beforehand. :shrug:
I think "shortened period of time" means less than a year. Even if it's only a few months that's plenty of time for a book release.
The kotaku interview? Updating the engine is what he said they were doing, post F3. How likely is it TESV's been near completion, since F3's release, and they've been optomizing the tech, for the last year and a half? When he mentioned 'work,' he followed that up with the tech speil. Just a thought.
I'd certainly believe that this game left pre-production near FO3's release but I doubt they entered beta at that point. That would mean they've been in beta for nearly two years
Todd also specifically says that some things may change which means they aren't in beta and the designers are still adding new content. If this is TES V they probably started kicking around ideas around TES IV's release, put it in to pre-production, and then moved it in to full production around the time Fallout 3 was done and most of the developers were freed up.