"Come what may" is an idiom. It means that no matter how difficult something is, you are still going to accomplish it. People in the U.S. still say it, but it is not a phrase that is used very often by young people. People who say it are usually middle-aged or older. In the U.S. it's usually used to refer to something in the future: Come what may, I am going to finish college. I am going to become a doctor, come what may. Our researchers are going to find a cure for cancer, come what may. Come what may, I will always be true to myself. If you are referring to something that occurred in the past, as in "I WAS/HAVE BEEN always true to myself," you could say: No matter what came my way, I was always true to myself. (meaning no matter what obstacles or difficulties you encountered) "Come what may, I have always been true to myself" sounds a bit unnatural to me because as I stated above, it's not usually used to refer to things that occurred in the past. However, if you say it, people will understand what you'mean.

"Come what may" refers to the future and "I have always been true to myself" refers to the past so a better way to phrase it would be "Come what may, I will always be true to myself". But "come what may" is not used in today's English, it is something that has probably only been used in older English literature books. Translating it into today's English would be something like "whatever happens" or "whatever comes my way", etc.

Not sure what the disagreement is about, but I'd agree with Coulson. Maybe it's not that antiquated, but more modern might be "Whatever happens" (or "will happen", same difference). In any case, the sentence and its use of tenses make perfect sense to me.

I disagree. "Come what may" is referring to the future, but "I have always been true to myself" refers to the past. "Come what may" is a very antiquated term, to change it so it'd all be in the past would be "Having come what would, I have always..." which sounds really strange.

“Come what may, I have always been true to myself” With a comma the sentence makes sense although it’s not something that people would say very often. It reminds me of something that would be written in an older book.