CiviCRM report for Case activities listing Case data
Are you using drupal? You might get what you want with a drupal view.

The "extended report" extension (https://github.com/eileenmcnaughton/nz.co.fuzion.extendedreport) has a case pivot report where you can filter on activity date for example. It might get you close.

A sideways thought: You mention upcoming scheduled so I assume there is a further end use for this report, which might be achievable other ways. For example scheduled reminders or civirules might be able to give advance notice when certain conditions are met.