Just because Tubelight failed that doesn't mean filmmakers like Imtiaz wouldn't take risk of casting him their movies. You're talking as if Salman is no longer bankable after Tubelight failure. One failed movie will have no effect on his stardom.
If Imtiaz offered Salman a movie then he will do it for sure. It will outdo JHMS at the BO. The reaction from SRK fans like you would be something like this