The latest rumint from South Korea suggests that the Samsung Galaxy S5 might get Android 5.0 Lollipop as early as December of this year. No official timetable from Samsung has been given, so take this intel with a grain of salt. There have already been some preview builds pop up online (one shown above), so it wouldn't be too surprising to see the latest Google OS come to Sammy's flagship that quickly.
Of course, Android 5.0 is a bigger departure/upgrade than folks might realize. Much of its 64-bit internal code has been optimized to run on a number of different devices, but that doesn't mean there won't be some bugs that need squashing. We'll keep an eye on things and let you know when we find something concrete.