Matt, a buddy of mine is in the same situation. He's had 1mb since it became available and was expecting to be upgraded to 4mb. 2 weeks into September he still hadn't been upgraded and contacted Telkom. He was told that the exchange he's connected to is not part of the 4mb test, so he won't be upgraded.
Wont be your router, chances are if your synching at 1mb youll be able to go higher... as masticore said, your exchange either isnt part of the test of your DSLAM hasnt been upgraded yet..