There is little known about future Jagex music however there was one song from MechScape released to the public by Jagex, this song was called New Beginnings and can be found here. This shows us that MechScape will definitely have music how much it will be like the RuneScape music system is still unknown. However since ThirdScape is being planned to be combined with RuneScape it seems that it will be unlikely for there to be any new music for it.