Add a comma after 2034 (both because you should separate a year’s number from the rest of the sentence with a comma and because the sentence is compound), and consider deleting in this year as unnecessary.
You don’t need the ellipsis after anymore, but it isn’t wrong, either. (It looks like a “dramatic pause” ellipsis of the sort one often sees in book blurbs or Netflix movie descriptions.) Whether or not you keep it, you still have to treat the end of the sentence as the end of the sentence: leave a space after whatever punctuation you use there, and capitalize the first word of the next sentence. It is the wrong pronoun there, by the way, because you’ve got a compound antecedent; change It is to They are.
Add a comma after them.
(The ellipsis after mistake isn’t needed either, and maybe one “dramatic pause” ellipsis per blurb-like thing is enough, yeah?)
It is the year 2034, and people do not have control over their dreams or nightmares anymore. These are now controlled by people in a factory creating each and every one of them, until someone makes a mistake…
(*rolls eyes* They’re not made in a factory; they’re carefully and individually handcrafted by skilled artisans. Everybody knows that… 🙂 )