I hope NONE of them are on the way out. I think they serve a purpose to their respective peoples...they are a link to it's history and traditions. In the case of Britain the Royals are a great boost to the tourist industry.
However, I don't feel optimistic about any of the remaining ruling Houses, particularly Britain and the Scandinavian countries...the Royals are more and more losing their mystique and many people are getting the idea that they are "just like us". It's fine to have the common touch to an extent of course, but once Royalty loses that certain "something" which even on the surface separates them from the people that they rule and soon you risk people questioning why have a monarchy if they are exactly like us in every way? It's a very slippery slope to a Republic when people stop seeing their Royals as purposeful, noble, dignified and ROYAL.
I am not an old fuddy duddy but I am old-fashioned enough not to want a Crown Princess who is the daughter of the local mailman and I don't care how lovely the woman is...I have said it before but the recent trend of the Crown Princes marrying commoners(and in some cases VERY common indeed) women is eventually going to do more harm than good. I think these marriages are okay and even romantic and great if they happen once in a while. But they should be the exception and not the rule. Marriages between Royalty and the nobility are now the exception, not the rule. So what happens if you have the children of these marriages themselves turn around and marry commoners and it continues on and on...then voila! Where is the link to tradition and history and nobility after a while? There is no bloodline to link or remind their subjects to their pasts. Sure, they might have a cuddly ruling couple who just adores one another and engages in delightful man on the street behavior(like making out in full view and giving revealing interviews to the media) but I feel in the long run this will do harm.