As for the EuCon Control Surface Plug-in, it's available for download for the SONAR 8.5 update support, and that article says it supports SONAR 7, 8, and 8.5. I don't know why it's not listed as a download under SONAR X1 support. I can't imagine that Cakewalk would take away support for the EuCon controllers in X1.
Maybe someone from Cakewalk will chime in. :)