I guess in future, we will have only dedicated class trains running for long distances
1) AC trains (premium and economy) - Rajdhani's, Shatabdi's and other premier trains will fall under this
2) Sleeper trains + General trains - Antyodaya and jansadharan trains with certain reserved coaches.
3) Mix trains - Short distance intercities/passengers with mix combo of classes (ACC, CC, 2S, DD)
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Other classes like Duronto, GR, Sampark Kranti, Humsafar, Uday etc will probably merge in one of above categories based on their proximity.