Most stylization parameters in line style datablocks are now
animatable by means of keyframes. Right click on a line
style parameter, and you will see a list of keyframe-related
commands in the context menu.
Concerning the implementation, RNA path resolution has been
extended to properly address color ramps in line style color
modifiers. File I/O has been also improved to load/save the
animation data associated with line style datablocks.
Known issue: Freestyle-related options in render layers are
not animatable at the moment, because of general inability (or
maybe a bug) that keyframes cannot be inserted with respect to
render layer options.