While it might be unusual for Canon to release 3 bodies in 12 months, these are unusual times.
2008: 1000D, 50D, 5D2
2009: 500D, 7D, 1D4
So, it's NOT unusual for Canon to release 3 bodies in 12 months. Not in the least.
And if you ignore calendar years, they've actually announced 4 DSLRs in a 12 month period - the 1000D, 50D, 5D2 and 500D were within 12 months of each other.
My comment was referring to the original post that said it was unusual and to be fair to that post, I took it to mean 'enthusiast and above' bodies. So say, 7D and above. Below that, the bodies are on a fairly fixed annual update schedule I think. But perhaps I misunderstood what was meant by that.
To further explain my point "these are unusual times" my thinking is that 60D and above are all due or overdue to be updated now or within 12 months which may not have occurred in the past, anyone know for sure? So based on coincidence of timing and combined with pressure from Sony at the enthusiast level, Canon (and possibly Nikon also) will want to refresh everything. Maybe I just want that to be true so looking for reasons to believe it
I don't believe they have any mandate to stick to a certain cycle. They will decide based on availability of new sensor technology (which is here now as we've seen with the latest Sony sensors), DigicV now in manufacturing, and market forces.
My prediction is that all 60D and above will be updated within 12 months along with something new such as another model in between or maybe medium format at the top end. Something is coming, I can feel it