Well, considering the underpinnings is XML, at least that's what I assume still, I hope that MS provides documentation for that, otherwise, write a spreadsheet up with these new features, then look at the underlying XML.
I know that there are tools out there written in both PHP and Python that convert CSV to XLXS, even with things like defining a cell as money or a date.
I'm sure those free utilities will be updated to account for these new features.
On the other hand, would have loved to be a fly on the wall in the features meeting on this!