Must. Necro. This.
sorry for reviving this thread - but am I right that this STILL is not solved by Envato?
I have recently discovered a few real gems on Themeforest/Codecanyon, but apart from some who include an update function into their themes (like Kriesi.at) the best you get is an email from themeforest when the plugin is updated, then you can manually download it and update it (with the usual hassle, deactivating, deleting, uploading via WordPress, losing settings, overwriting via FTP, messing up things... )
Is there a working 3rd party solution in the meantime to really AUTO-update plugins from this marketplace?
thanks a bunch!