[Update 12/16/2015 – This has been answered! Microsoft will keep the promise of unlimited storage for OneDrive for Business! See this blog post from Microsoft for more details:
I’ve been asked that question a lot lately because of some recent headlines. The official answer today is that you get 1 Terabyte of storage. This is from the official service description (here).
However, almost exactly 12 months ago, Microsoft announced “Today, storage limits just became a thing of the past with Office 365. OneDrive and OneDrive for Business will now offer unlimited storage—at no additional cost—to our Office 365 consumer and business customers.”
Reference #2: https://blog.onedrive.com/office-365-onedrive-unlimited-storage/
On the official Microsoft Roadmap site the Unlimited storage promise is still listed as “In Development”
“Moving forward, all Office 365 customers will get unlimited OneDrive storage at no additional cost. In the meantime, get started using your 1 TB of storage today by backing up all those work files kicking around on your PC – with the knowledge that even more storage is on its way!”
Then recently, Microsoft announced that the consumer versions will be limited to a 1TB limit and will not get the ‘unlimited’ promise.
According to a prominent Microsoft reporter, Microsoft could be releasing a revised roadmap by the end of November 2015.
Even if Microsoft was to keep OneDrive at the current limit of 1TB, that would still be enough for each business user to store 1 million Office documents or 330,000 photos, based on an average file size of 7Mb per document, and an average photo quality of 9 megapixels.