IIRC the last SONAR survey didn't include color customization in the response options for the "What improvements do you want to see?" question, so I guess the current look will last for a while.
I personally love the X1-2015 look, except for the colors of the FX Racks introduced this year. Sadly, these colors are also unlikely to change for a while, as we haven't seen the plan appear in the Up Next section even months after many users (47 so far) supported the request for it:
http://forum.cakewalk.com/FX-Stacks-Improvement-m3153747.aspx Lynn
I would personally like to see better contrast in the control bar lettering, at least. Please make all the letters white if nothing else, CW.
It seems to me that the text in the CB became a little brighter in SONAR 2015. I no longer have X3 and prior versions installed on my system, so I can't compare. But it would be nice if we could customize the color.