Another one of the more obvious potential storylines would be pregnant Penny. That could be sensational. Juggling her career, a baby and Sheldon would provide some hilarious moments for sure, and it would be a sign that the show has 'grown up' to an extent. We've already seen a vision of Penny while she's pregnant, but there's every chance it could become a reality by the series' end, with Bernadette pregnant and... Well, you can't rule out Amy now, can you? All of the characters are approaching a potential crossroads on that front.