Yesterday, I analyzed ThemeForest and Envato's new Hosted program for getting hosting alongside your theme. Vova Feldman has a really interesting blog post that's a good companion to what I wrote, which dives into the financial opportunities that still exist on ThemeForest. In short, he concludes that the “gold rush” is not over.
However, it can be more difficult to be seen out of the gates. Most themes don't sell a whole bunch of copies, and like most marketplaces, the top sellers make up a majority of all revenue. But for the right product, or the right situation, ThemeForest can still be a great option.