Besides Africa, you'll still find these in use throughout the world by smaller defense forces & in even some of the larger rising powers such as India. According to Global Security, India has been overhauling their 700 T-55 tanks with plans to use them until 2017. Iraqi forces still use them today as does Pakistan. Heck, with the way things are going in the Afghan / Pakistan region, you may get the chance to see a Leo or Abrams take out a few in the near future. Serbia currently uses an upgraded model & you'd certainly have no problem teaming a Leo up against a Serbian T-55 in a replay of the Kosovo action.

Keep in mind that the T54/T55 has the distinction of being the most mass-produced tank in the world so they'll be around a while.