I vote for iBook. Seems like a great name they may have retired from the laptop lineup in order to resurrect it for the tablet. Also fits the e-reader aspect very well.
There is no way it is going to be called iBook. Why would they want to make it sound like an old product? Not to mention that it's not really a book-shaped object to begin with (i.e. it doesn't open and close). They retired that name from laptops so that all of their computer products would have Mac in the name.