Yes, all future event cards will become available through tickets at some point, and no, you don't have to have any copies of the cards you intend to craft already. Not all, but likely the majority of people who own 4 copies of every card, have at some stage, paid real money. Unfortunately, the game currently seems to be weighed more heavily in favour of these people in comparison to other digital card games, by increasing the amount of super rare/legendary cards, while making them no easier to acquire in-game. With all hopes, the game will become a little more friendly towards people like me who prefer to remain entirely free-to-play, before we're all drowned out by the vast size and speed of which the future expansions arrive.
I wouldn't worry about getting all the event cards as much as getting all the other cards which don't show up each week. If you intend to acquire 4x copies of all, I can only imagine that you'd need astronomical amounts of in-game time or to pay some real money.
