I would love to see a new certified masterkeyboard for Sonar. So it has that ultimate driver and is 100% supported. 

My guess is that will not happen unless Gibson happens to own a keyboard manufacturer.  Gibson owns Cakewalk and has Cakewalk concentrating solely on software.  Notice the site does not have any hardware products listed.

Muziekschuur at home
I would love to see a new certified masterkeyboard for Sonar. So it has that ultimate driver and is 100% supported.

You can make one yourself! Find the keyboard you like, with keys of your taste and physical control types you need. Drivers are normally not an issue for such devices. Then you just need to integrate it with Sonar the way you like.
Since you mention SI-24 in your signature, you can check how it works there: http://www.azslow.com/index.php/topic,316.0.html
Note that EVERYTHING can be changed/extended (with anything you can find in any Sonar Control Surface) and NOTHING is particular device specific (f.e. Si-24 preset can be reconfigured to work with any masterkeyboard... as long as it has sufficient number of controls)
 
PS. And if you decide to give up before finishing the preset, as many other do, at least you will know why CW do not bother to offer such solution