CardDAV is very much not a new standard. It's been around for at least a decade and is based on vCard which has been around for even longer.
That said, I'm glad they're doing this now. For the longest time the only way to sync contacts on iOS has been to set up google as an exchange provider.
Google Sync via ActiveSync/Exchange has some serious limitations:
'Limited Contact Information. The iOS device can synchronize up to 3 email addresses. Phone number synchronization is limited to 2 Home numbers, 1 Home Fax, 1 Mobile, 1 Pager, 3 Work (one will be labeled 'Company Main') and one Work Fax number.'
Yes. The Exchange/ActiveSync version Google uses is quite old and fairly limited in the number of elements available per property, the labels are only a fixed set, and some properties are not supported at all. CardDAV doesn't have these limitations.
CardDAV is much like CalDAV and WebDAV - but for vCards - which has been around pretty much forever.
Interesting fact: Apple appears prominently in the RFCs of two of the three protocols as well as the vcard format.
With vCard and CalDAV, open-source productivity software never really did much better than Microsoft Exchange/Outlook, but CardDAV does provide something that Exchange doesn't - an working, standards-based way to sync your contacts across all accounts.
That said, I'm glad they're doing this now. For the longest time the only way to sync contacts on iOS has been to set up google as an exchange provider.