I'd like to bump this up from the grave for an update from ESRI.
ArcGIS Explorer Online is built on a Silverlight platform so we all know that it's a platform on its way out. Based on information found on this page on ESRI's website, they indicate that they are in development of a desktop version of Explorer for ArcGIS. Lord only knows when this graphic was last updated so it begs the question- what is the status of this development and when can we look forward to a desktop replacement version of ArcGIS Explorer Online?
I still use Explorer Online on a fairly regular basis and would hope that I'm not the only one.