I think routes like Bombay - Ahmedabad or Chennai - Bangalore, Chandigarh-Delhi can take in multiple classes of trains, but not other routes. I am interested to see what they will do on the NDLS-LKO route. That route, sooner or latter will get a VB. It already has a three decade old Swarna Shatabdi running. A Tejas in reverse direction was recently introduced. I assume they would retire the Tejas in favor of VB.