Based on the Apple page, http://www.apple.com/macosx/technology/
It looks like Quicktime X is a refinement (like all things in Snow Leopard) of the existing quicktime technologies, it's likely that Quicktime on Windows will get similar refinements, but will keep the Quicktime 7 player, or maybe Quicktime on Windows will gain the Quicktime X player as well.
The player itself has never been what supports the formats, it has always been the underlying quicktime system components, and in the era of system 7/8/9, a popular thing was to use quicktime player 2.5.1 or so on system 9 with quicktime 4/5/6 installed, which gave you all of the format support of the most modern quicktime, but with cool things like looping and very simple editing.
As far as Quicktime X supporting new formats -- it might, it definitely adds such things as GPU-acceleration, a few new http streaming things, and more integration with OS X technologies like CoreVideo, CoreAudio, CoreAnimation, and Grand Central Dispatch.
It looks like Quicktime X is a refinement (like all things in Snow Leopard) of the existing quicktime technologies, it's likely that Quicktime on Windows will get similar refinements, but will keep the Quicktime 7 player, or maybe Quicktime on Windows will gain the Quicktime X player as well.
The player itself has never been what supports the formats, it has always been the underlying quicktime system components, and in the era of system 7/8/9, a popular thing was to use quicktime player 2.5.1 or so on system 9 with quicktime 4/5/6 installed, which gave you all of the format support of the most modern quicktime, but with cool things like looping and very simple editing.
As far as Quicktime X supporting new formats -- it might, it definitely adds such things as GPU-acceleration, a few new http streaming things, and more integration with OS X technologies like CoreVideo, CoreAudio, CoreAnimation, and Grand Central Dispatch.