When the world tilemaps are not the same size as the tilemaps isn't creating levels harder when you want to view 1 screen at a time which now contain multiple world tilemaps? Or am I thinking to much about zelda now?
Otherwise your worldmap is again a different size from the levelmap???
From what I understood, the "world pages" Casey talked about are only there for achieving sparseness -- there won't be as much of a concept of discrete tilemaps like we have now. The key to this is due to the coordinate packing he talked about, which allows us to treat the world like a continuous grid. There's not really a strong concept of a given tile being "in" one page or another, except when it comes to defining pages initially.
So yes, we could have "screens" which have multiple world pages in them. And probably will, if world pages are square (since our screen is decidedly not).