Four months ago, WordPress user Fredelig created a new ticket on WordPress trac suggesting the plugin update notification bubble load the page listing all of the plugins with pending upgrades.
In WordPress 3.9, clicking the notification loads Plugins.php which lists all of the activated plugins, including the ones with upgrades. This requires a second mouse click to show only the plugins that have an update available. Although it was too late to include in WordPress 3.9, it’s also missed the boat for 4.0.

On a related note, I’d like to propose an enhancement to the comment notification bubble. Clicking on the notification currently loads edit-comments.php which displays both approved and moderated comments. Ninety-nine percent of the time when I click on the notification link, it’s because I want to approve a comment pending moderation.
Although the task can be accomplished with the way it works now, sometimes the comment I need to approve is not on the first page and I have to click the Pending comments link. Having the notifications bubble load the pending comments first would save me a mouse click.
Do you have any pros or cons regarding the suggested enhancements?
In the meantime, could the necessary html changes be implemented via add_filter?