Eric Kripke said he is prepared to reveal what caused the blackout before the end of the Show:
"You should look for clues everywhere. There was a phenomenon that we have up our sleeves as to what caused the blackout. What you see in that globe shot [of the blackout creeping across the Earth] is an accurate representation of what we’re working on. Currently, in the writers room, we’re talking dangerously about revealing that secret before the end of the first season."
"The longer you drag out an answer the more pressure there is that it’s the greatest answer given in the history of man. Frankly, I’m not that smart. I’d rather answer a question and open a door to a bigger room. Even if we do answer the question of what caused the blackout it leads directly to a bigger and scarier mystery.”
Kripke also confirms that the search for Danny boy wont go on all season (with Episode 10 said to be significant in that regard), Charlie’s first quest is largely a means to introduce the audience to the world and characters