Yeah, if it becomes common enough, I suppose you are right. But since this is a whole class of "phrasal verbs" that all have the same rules, it seems less likely that that is going to happen any time soon, as opposed to something like "all right" changing to "alright" which is more of a discrete case.
There is also the issue that phrasal verbs are often split up or rearranged ("when will they shut it down?" "it is shutting down", etc), which isn't all that compatible with merging into one word.
Anyway I'm glad to see they changed the title on HN, even if I got downvoted for my complaint. :) I appreciate your pointing out the value of this discussion, though! ("it's these sorts of debates that determine what the end result will be.")
I'm personally ok with the non-literal use of the word "literal," but that's a different tangent...