NOTE AS OF FEB. 21, 2014: The basemap system upgrade to ArcGIS 10.2 for Server occurred last night. See Basemap System Upgrade to ArcGIS 10.2 for Server Completed for the latest information on this update.
The Esri ArcGIS Online Basemap system (i.e., services.arcgisonline.com, server.arcgisonline.com) is currently operating on ArcGIS 10 SP1 for Server. We are in the process of upgrading to ArcGIS 10.2 for Server. When determined, an updated schedule will be posted on this blog. See Esri Basemap System Upgrade to ArcGIS 10.2 for Server for details about the new capabilities in ArcGIS 10.2 for Server and specifics regarding case sensitivity on map service URLs. Change to World Topographic Map sub layers provides information on a related change to the sub layers in the World Topographic Map.