NOTE: Update 4-30-14 - This has all changed as we now provide 1TB of default OneDrive for Business quota per user. Please see new my new blog post here and ignore the old scenario below.
Great news you can now up your SharePoint OneDrive for Business quota to 1 terabyte up from the default 25GB and previous upper limit of 100GB.
The way it works is you can specify which specific users you want to assign new upper quotas of 50GB, 100GB, 250GB, 500GB or 1TB quota. The catch to this is once you exceed the default quota of 25GB for a user you will be pulling storage out of your overall pooled tenant storage allocation (10GB + 500MB x total number of users) in your tenant.
If you have 10,000 A2 licensed users that equals 5TB of pooled tenant storage available.
You decide to up OneDrive for Business quota from default 25GB to 250GB for 4 users which consumes 1TB out of the 5TB leaving 4TB remaining of the overall pooled storage.
You can purchase more pooled tenant storage at a per GB / per Month charge if you require more.
The SharePoint site collection limit has also been upped from 100GB to 1TB max and the 25TB max SharePoint Online limit in a single tenant has been removed which means you can purchase as much pooled storage as needed in your tenant.