Some thoughts how to improve ThemeForest and it will be great to hear a response from Envato team and WP authors.
1 - Paid Submissions - As author I find a submission fee for WordPress category is the real solution for reducing a number of submissions and increasing a quality of themes. Envato will get extra money. Authors will get reviews faster.
2 - Paid Updates - As buyer I really do not like when another one purchased theme became abandoned/removed because of low sales. And I do not blame author because I understand him. He must be motivated to continue work on the theme, however the current business model focused on new buyers only and doesn’t protect author and current buyers as well. No new sales >> No updates >> Angry buyers & Upset author. This business model is not sustainable.