Today I learned that the statues are getting moved to set up a staging area for a subway route. It seems that the move to the Karl-Liebknecht Bridge (50 meters south, facing to the west). Apparently, the plan is to return them in 2017.
Hopefully they won't be replaced with some long-gone historical reconstruction, though it would probably surprise nobody if (as in the case of the recently demolished Palast der Republik) wealthy westerners sought to do away with the DDR-relic.