As a Norwegian I'm a bit conflicted. Yes, the latest poll has shown that teens don't find the monarchy interesting - but, these boards aside, how many teens do?
Considering that Haakon is one of the ones in the family with a fairly high approval rating, along with his father, - I don't see the monarchy disappearing in the first generation. I think that many Norwegians are much like myself, we know what we have - we don't know what we'll get.
Also, the royal family isn't as unpopular in Norway as I've seen it portrayed in this thread. There have been incidents, but haven't there been so in every royal family?
The republican sentiment in Norway isn't high, despite the incidents, of which there haven't been so many that someone would think of changing the form of governments just because of that.
Harald is our king, and he really proved himself to be that when he appeared in hurricane-destroyed parts of the country in 1992, way before any national politician did. (The Prime Minister's office, by the way, sent a reprimand, as they felt he was stepping over his line...) People had his doubts about Harald before then, as he hadn't been leading the people WWII as his father and grandfather, and it was felt that he had been living in his father's shadow, but that cemented a good reputation.
Should Ingrid Alexandra not want to take on the role when it is her turn, or get too political, or involved in scandals, I think we might be talking about some change, though. But as the current situation is, I doubt it will happen in the immediate future.