Yes it happens. Drupal 7 will not only rock the world of APIs, but also get a new shiny wrapping. Of three core candidate themes, two have still survived and have gotten pretty far along the road. These are the Bartik theme and Corolla theme
The news that we - hopefully - get new themes could be very exciting. It all started with removing from core Bluemarine, Pushbutton, Marvin and Chameleon and detecting - there was only Garland left! The idea of having an almost completely rewritten Drupal with still the same theme from Drupal 5 was sufficiently horrible for the designers to start their engines.
Jen Simmons took the leap and boldly put Bartik into the issue qeue. Let's hear it for Jen - this was the crucial step. Motivated by that, Jarosław Foksa (Jarek) also showed some courage and dropped in Corolla.
When you look at the Corolla issue queue and the Bartik issue queue - well, you will notice some difference. Corolla only has three open issues, but Bartik at least thirty. So there is a lot more activity behind Bartik, and I am not worried it will make it into core.
But what about Corolla?Jarek is not as well known in the Drupal Community as Jen is - and so he has a harder time to get people behind the project. Also he did the bunch of the work by himself, which may not be the cleverest thing in the adventure park called Drupal issue queue. It once more taught me how you get things done in the issue queue, which I always like to refer to as the Tom Sawyer Principle : Try to raise interest in the issue, so you do not end up having to do it alone.
So if you are a designer or/and themer and you think that three themes in core are better than two - jump in and help out t get Corolla ready.