While definitions vary from critic to critic, most agree that "sensawunda" is some sort of paradigm shift (a phrase from John Clute and Peter Nicholls, but not an original phrase) in much the same way as the phrase is used in science: a change of our basic assumptions about something (in this case, literature and reality). If that be the case, then "sensawunda" in science fiction relies entirely upon the genre's speculative elements, since anything that does not shift us from the present in a fundamental way cannot produce the effect (at least for most).
But now we run into a problem with the concept. Science fiction has largely become a self-referential genre. While the intention of authors is likely not to look to the past of the genre, that doesn't change the fact that almost everything in contemporary science fiction has already been done before. Contemporary science fiction is, for better or worse, a genre that is always looking to its golden past, always conjuring images and ideas presented at a time when the genre inspired and shocked people based solely on its ability to present a vision of the future not found elsewhere (wondrous or terrifying futures, depending where you looked). And if science fiction is self-referential, replicating the same references without realizing it is doing so, then "sensawunda" no longer functions. It can't--at least not for those who are well read in the genre. "Sensawunda" relies on some new thing (the novum) that draws us out of our comfort zone of reality and gives us a new reality, one tinged with the speculative details of a future that may or may not be (science fiction has never been a predictive genre). But this can't happen multiple times for the same thing in different formats (i.e. different authors writing about the same concept). We've already seen it. The surprise comes, perhaps, from the movement of the plot, but that's not something isolated to science fiction, let alone genre fiction.
If all this is true, then that means "sensawunda" is dead for the old, and lively for the new in almost all cases. New readers certainly feel the moment we all secretly mourn, while old writers continue reading for...what? What is it about contemporary science fiction that keeps us reading, despite the near bi-monthly pronouncement of the genre's death? Why do we still go to science fiction movies? Why do we want to see a possible future when we crack the first page of a new science fiction book? It's not "sensawunda." I suspect we're all aware on some level that the "sensawunda" is gone--although, maybe it still exists in the movies simply because they visualize things we've only dreams about or read in books.
I suppose the question I'm asking is whether we're reading science fiction because of loyalty to the genre, a perspective we've adopted within ourselves that constantly looks forward (even to the bad), or simply an interest in the furniture of the genre (spaceships, aliens, future technology, and so on). I'm a pessimist, so I lean more towards the last of these by default. But I could be wrong. Maybe we are loyal to the genre and in possession of that future-oriented mentality.
What do you think?