With "catenative" verbs like postpone, the form of the following verb may be either an infinitive or an -ing form or both, depending on the first verb, and with no obvious pattern. In this case, only #1 is correct. org/wiki/Appendix:English_catenative_verbs
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ljswaveOne more thing, Is #2 always wrong sentence?Yes. It would startle any native speaker.
ljswaveI mean that someone omits to say the object (=going to the music concert). Can it be possible or natural ?No, that would not be an acceptable ellipsis.