Your question has no simple yes/no answer.
Your first sentence is correct. It is correct to say:
The newest show has these known actors in it.
The pronoun "it" tells us what these known actors are in, i.e. they are "in it"--in the newest show. It would be cumbersome to say:
The newest show has these known actors in the newest show.
We substitute the second "newest show" with "it."
Your second sentence is incorrect. However, it would be correct without the pronoun if you left off the preposition "in."
This is correct:
The newest show has these known actors.
I would, however, expect to see a list of the actors because you say "these...actors." If you want to exclude the list, you can substitute the word these with a word indicating how many actors there were, such as some, several, or a few.
That sentence is correct but it has an unfinished feel. A way to get around all the above problems is to write it this way:
There are known actors in the newest show.
That way you establish the existence of known actors but do not obligate yourself to name the actors. Nor does it contain the questionable preposition and pronoun. On the other hand, if you want to preface the list of known actors in the newest show, you may want to say:
In the newest show are these known actors:
Then list them.
The colon is needed to set off the list.