Sentence #1 is correct. Sentence #2 could also say, "It it hasn't happened by now, it's never going to." or "... it's never going to happen." or, as stated before "... it never will."

Hi. Sentence #1 is good. However, sentence #2 can be changed to "If it hasn't happened by now, it never will."

The first sentence is correct. The second sentence 'If it hasn't happened by now, it's never to.' is not correct as 'it's never to' is a broken sentence.