It shouldn't crash. And it should support Xinerama. In the current state, only ati and intel seem to support randr-1.2. All other drivers need Xinerama for multihead configurations. Think of the case where you want to use an intel card and another card with a non-randr-1.2 aware driver.
So as long as most of the drivers don't support randr-1.2, Xinerama should still be a supported feature.
I currently use the old i810 driver that I patched to build against the current Xorg 7.3 headers to get Xinerama working. However, this only works because my hardware (i965) was already supported by the i810 driver.
It shouldn't crash. And it should support Xinerama. In the current state, only ati and intel seem to support randr-1.2. All other drivers need Xinerama for multihead configurations. Think of the case where you want to use an intel card and another card with a non-randr-1.2 aware driver.
So as long as most of the drivers don't support randr-1.2, Xinerama should still be a supported feature.
I currently use the old i810 driver that I patched to build against the current Xorg 7.3 headers to get Xinerama working. However, this only works because my hardware (i965) was already supported by the i810 driver.