I agree. They need to get a jump on it as all governments move slowly. I think they last thing they want is the legislation passing after the birth.
Actually I think that would be the best thing, wait until Catherine gives birth and then change the succesion laws. If it's a boy then no one has to bother for another 60 years, if it's a girl then pass the law. Simple. Countries in the commonwealth have bigger issues to deal with.
I don't think that is the intention here. My take on the "rush" article is that it will be rushed through the British parliament in the two-weeks timeframe. If I understand correctly, the other parliaments cannot even consider the legislation unless/until it is passed by the British parliament. So this is the "jump-start" to get things moving.
They can consider legislation prior to something being passed in the UK courts. However in December it had been agreed that the UK would draft legislation first, but would not introduce it to the government until all 14 realms had agreed to the terms of the new legislation (roman catholic bit, limit line of succesion that asks for marriage permission etc). Also, even after they receieved agreement, the UK government would not go ahead until the other realms had their domestics situations in place for the change.
For instance in Australia, for new legislation to be created they have to amend the constitution and that requires a referendum. In mid decemeber some disagreement arose about how the country, and the separate states should go about this. Nothing has been resolved and a bill (on what i'm not sure) is supposed to arrive in parliament in 2013.
Canada is also a whole different ball game, all the provinces and the federal government must agree to the changes.
New Zealand is fine and dandy apparently, just needs to implement a few changes which will occur in 2013.
As for the UK, to "rush" this act through, they need parliamentary time and as of the start of December when the bill was drafted, there hasn't been any time allocated.
Everyone needs to agree at the same time, the legislation needs to be brought to law at the same time so that any baby boy or girl will have the correct succession rights in all 14 realms. We can't have a situation where a girl in first in line in one country, but her younger brother is first in line in another can we?