The exact date of the required update is currently not available from Authorize.net, but we are diligently working on upgrading all our plugins to meet the requirement. The date for this change will be announced by Authorize.net later but is expected in the next 2-3 months.
More information about the update requirement can be found in the Authorize.net developers forum here.
The updated version of several of our nopCommerce plugins have been completed and are available for purchase on our web site. This version has been fully tested in both the sandbox and a live environment is OK to use starting immediately.