They will only be empty for a short while once they are able to fill up again with posts, and it needed to be done to fix errors where people end up going to the "Page not found" page when trying to view a topic.
Until then you can check out new posts by pressing the "Browse" tab at the bottom of the screen. It's an excellent way to do that as well.
The good news it that the titles are upgraded, fixed, and load the pages faster. They are more search engine friendly as well.