CSS Transitions should be able to animate all animatable properties, not just ones with explicitly set values. Right now those properties are excluded from any transitions.
I could imagine just allowing the "all" value to include properties with "auto" values, or perhaps another keyword could be added like "auto" or "all-auto" so that the current behavior could remain unchanged and this would be an optional feature.
I looked around to see if there was discussion on this issue and didn't find any, but feel free to point me towards any I might have missed.
*** This bug has been marked as a duplicate of bug 16020 ***