According to Micorsoft's Office 365 roadmap, OneDrive for Business Sync for Mac client is still under development. Microsoft is also working on other improvements to OneDrive for Business and Sharepoint like being able to use % & # in the file name; longer file name support. As mentioned before, the beta was suppose to be out at the end of 2014. The beta might have been just an internal or limited release beta so that's why most people have not seen anything. Also with some beta releases, the users will have to sign a Non-Disclosure Agreement so they cannot mention anything. I had to do that for betas product releases in the past.
If you are interested, here's the link to the Office 365 Roadmap. office.microsoft.com/.../office-365-roadmap-FX104343353.aspx
Here is the file limits as described by Microsoft: support.microsoft.com/.../2933738
Number of items that can be synced
You can sync up to 20,000 items in your OneDrive for Business library. This includes folders and files.
You can sync up to 5,000 items in a SharePoint library. This includes folders and files. These are the libraries that you find on various SharePoint sites, such as team sites and community sites, libraries that other people created, or that you created from your Sites page. This also includes syncing other people's OneDrive personal sites that you may have access to. You can sync multiple SharePoint libraries.
Size limit for syncing files
In any SharePoint library, you can sync files of up to 2 gigabytes (GB).