Did you know that WordPress.com doesn't blog about third party themes any more? It's been that way for a few months now.
I started following a new Twitter account called @wpcomthemes so that I can keep up with new releases. The account tweets both Automattic and third party releases, which have still been released on a weekly-ish basis.
All in all, I counted 139 commercial WordPress themes now on WordPress.com. Of those, I counted 36 commercial themes from Automattic. So we've recently passed a threshold of 100 commercial themes by third parties, and who knows how many free ones.
You can check out all WordPress.com themes here. Finding a full list of third party themers is a challenge, though the authors themselves have a better understanding of how their themes are doing (and maybe how they're doing against others).
I know for a fact that when I counted early last year, one or two theme shops appeared to have done close to a million dollars in revenue on WordPress.com; then they took down the stats of active blogs using a theme, and I don't know any more.
A number of theme companies are relying pretty heavily on the WordPress.com marketplace for sustaining sales that seem to be nearly universally declining on self-hosted installs — outside of marketplaces like ThemeForest.
By the way, Envato did their year in review as well. It's nuts.