I suspect that it will drop off in a day or so. I think its just people taking the opportunity to show of their creations while "show HN" has a high profile.
If not I'm sure they will tweak the ranking algorithm to get them to drop off the home page a little more quickly. They would still be on the show page. This is what already happens to some extent will all "self posts" (ask/show/no url).
If not I'm sure they will tweak the ranking algorithm to get them to drop off the home page a little more quickly. They would still be on the show page. This is what already happens to some extent will all "self posts" (ask/show/no url).