Four Terabyte Content Databases with Microsoft SharePoint 2010
With annoucement of SP1 for SharePoint 2010, now Content Database size can be raised to 4 TB. This means you can extent current SP 2010 site collections to 4 TB also.
Also for record center and document center there can be exceptions. This document from Microsoft provides details and how to manage large terabyte databases in SP 2010: http://go.microsoft.com/fwlink/?LinkId=223599