Flightcraft is in the process of replacing all of its 100's with 200's. We only have around 4 100's left online I think, and are buying more 200's everyday.
Purolator wants an all 200 fleet eventually, transition should be done in a couple of years I assume.
As for how long we will fly it ... Hard to say, lots of rumours about 757's here, but most believe that it will be at least 5 years away with a slow transition period again.
Seems the consenus though that 57's will be the replacement.