Ann: Yowie Secures New Manufacturing Agreement, page-63

Ferrero aka Kinder Surprise can enter the US anytime they want. They have deep pockets to pay any licencing fees or patent infringements for the yr or 2 before the patent runs out. They also have lots of products, i've seen plenty of kinder marked chocolate bars etc in stores in Perth. They could also make bigger eggs and products if they wanted to, I'm pretty sure i've seen bigger eggs as well from them.
They could also afford a longer lead time to market penetration & profitability.

So there is no real roadblock to them competing with Yowie in the US except that for whatever reason or perception (that could be overcome if they really wanted to) it appears it does not fit in with their current business strategy or model. Whether thats still the case a year from now, who knows?