usage of "yet to be"

I think this could be construed to mean something different, depending on context. It could actually be a rejection of the notion that the person mentioned is or will be a murderer.

For example,

Mr. Johnson may be many things, many of them unpleasant: a career criminal, a liar, a deadbeat husband. But he is yet to be a murderer.

This means that whatever bad things he has done, he has stopped short of murder. It is the kind of statement a defense attorney might make in a trial on behalf of his client. Sure, he's a bad man, but he's not a killer.

The word yet, when used as an adverb, means that something has not occured at a particular point in time

up until the present or a specified or implied time; by now or then:
I haven’t told anyone else yet
aren’t you ready to go yet?
I have yet to be convinced

In each of the examples, there is a connotation that the situation is likely, or at least potentially, about to change.

Most US speakers would read the example given to mean

He is yet to be a murderer [but I am not sure how long that innocence will last].

If I were to proclaim proudly

I have yet to cheat on my spouse

my wife would take it ill. She expects nothing less than

I have not cheated on my spouse, or better yet
I would never cheat on my spouse.

Robusto's answer shows the valid present interpretation of 'is yet to be' - how can one possibly be certain what is yet to be or what someone is yet to do (unless one is a prophet).

However, there is the possibility of using the present tense to refer to a historical event or time interval:

In 1928, Hollywood is yet to be discovered by the Marx Brothers.