I'd love to see an automated strike zone. But I think it is still a ways out on the horizon. On the bright side, with Pitch F/X and the old QuesTech, the strike zone is getting better. Better to the point that Cole Hamels complains that they don't squeeze rookies anymore.
As for more instant replay, let's just get the calls right. If it takes an ump in the booth, or at MLB HQ, or just more umps getting help when needed, I'm all for it. As for replays and challenges, it works well enough in the NFL that I am sure that MLB and the players could work something out.