Classic Sonic format coming back would be a dream come true for me. Unfortunately, Sega would rather eat their shoes than retrogress. It seems that although the Sonic Team would love to work in classic format, Sega wants them to push their fancy new technology (e.g. 3D models, HD quality levels and cutscenes, voices for characters, etc).
It may also be worth taking into account that a lot of people really like the new format of Sonic. I, and many other people, however, just keep living in the now-distant past with our Geneses (What is the plural of "Genesis?") and drown out the surface world.
All in all, Sonic Generations will probably be Sega's most successful Sonic game, as it appeals to a much wider audience than ever before, and is across multiple platforms. It will be nice to see Sonic restored to his former glory, if only temporarily, then fade into the shadows once more.