texture sizes are pretty important, especially when it comes to texture passes and such. For example, with normal maps, parallax maps, opacity maps, color maps, specular maps, incandescence maps.... lots of possible textures all for just one object. So, while next gen systems might could possibly use a 1024x1024 color texture, if they are using all these different maps... and if they're all the same size... that adds up! So, I imagine 512x512 is probably more accurate a maximum texture size for most things.

Hope you like the book.