iOS Developer Account - 50GB iCloud space still available. Will it go away?
This is part of the mail who sent apple regarding this:


  Your complimentary 50 GB of iCloud storage is expiring on November 1st and your account will be downgraded to your original storage plan. If you are using more storage than your original iCloud storage plan, you need to upgrade your plan or reduce the amount of storage you're using. You can view your storage used and upgrade your plan from your iPhone, iPad, iPod touch, or Mac. 


So, it will expire in a few days. Did not say anything about how will they do if you are over quota, just tell you to upgrade or free space.