I don´t think that Felipe and Letizia are posing. The photos which I posted are just one little moment of what happened last night. The photographers take photos all the time and they get almost every glimpse of the pair to the film. There are also different kind of photos from last night, like this:
Felipe and Letizia know very well, that all the photos will be in the various agencies´ websites shortly after the event. So if they were posing, I guess we wouldn´t see "normal" photos of them at all.
But I think that they are in love, and why couldn´t they show it? People are different, the royal couples are different. They show their feelings in different ways.