The video app just uses the 940 driver and binary blob, to which we always had the documentation and API. nothing really interesting. (The source of the player side of the video app was released a while (>1 year) ago)
I can't really think of a good reason besides updated wifi and SDIO drivers to move to 2.6.. 2.4 has better performance for single-CPU low-memory systems, I believe.
And, let's face it: there's little reason to use SDIO and wifi on a device like the GP2X that has such limited resolution. Web browsing is a pain and if you need console access for development on an F200, you can just get a cradle + serial cable. (Though cradles might be harder to come by and you'd be better off finding a nice used F100 with a busted joystick or something for development.)
It'd be a large undertaking with little reason to do it.