Google Maps now uses vector maps (rather than bitmap tiles) which allows much more data to be stored offline (esp. useful for preloading navigation).
They also allow 3-D buildings and rotations as a result.
See online.wsj.com/video/google-an ...
I suspect they'll slowly move the desktop Google Maps version to use this format, especially for those browsers that support WebGL or SVG.
That also means you will need a strong computer to go on Google Maps because all the data, which was previously generated by the map team as JPG files, will have to be done by your browser...
Well, I don't think the tile servers are going to die for many years. There are many maps clients (e.g. the Symbian Google Maps app) that rely on tiles and aren't necessarily auto-updated. So the bitmap option will probably remain for as long as possible.
Also, the satellite images will still be image tiles. I wonder how it handles the satellite/hybrid view while in 3D mode.