"What's in a name?" More like "What's in the game?" So long as it is at least as thrilling and terrifying and thought-provoking as the original BioShock, doesn't matter to me what they choose to call BioShock 2.
And speaking of BioShock 2, 2K has announced that the game - now widely whispered to be coming out this October - will be released for Xbox 360, PlayStation 3 and Windows PC at the same time. Which will make lots of people very very happy :-)