As I said in another topic, it's unlikely that this will affect premium modules since the master server is hosted by Bioware, but it might go down someday, so it's probably a good idea to try to unlock premium modules while it's still running.
The reason given for discontinuation of service does not indicate anything to do with Gamespy.
"But as games get replaced with newer titles, the number of players still enjoying the older games dwindles to a level -- typically fewer than 1% of all peak online players across all EA titles -- where it’s no longer feasible to continue the behind-the-scenes work involved with keeping these games up and running. We’re constantly working to keep our games and services available for as long as possible."
The date seems too coincidental to be thought of as not linked to Gamespy.
My conclusion when reading this is that the service no longer being provided will include the shutting down of servers that assist in Gamespy connections. This may mean that our Master Server might be accidentally included in this effort.
If you have a source telling you that the Master Server will not be shut down by June 30th make sure that the source has contacted the higher ups in EA. I can just see an accidental loss of premium module support followed by a cover up of dead silence.