There is no last guest. There are infinitely many guests.
I have trouble with that, though - if there's a "first guest", then I don't see there can't be a "last guest".. "room 1" and "room n" (as the article labels them) are equally arbitrary if there are infinitely many.
In that case I'd probably rephrase my original objection to say the "next guest" has nowhere to go, except when the they depend on the "next next" (etc.) guest finding a room in a "full" hotel - but I can see how that situation "never" comes up since they can pass the burden along infinitely.
I just feel like someday at the end of time, this poor unassuming new guest is gonna get cheated out of a room..