What are your thoughts on the Navy, Marine & Airforce changes to their maternity leave policy? Do you think the Army will follow suit?

I think whatever the policy is, it should be universal across the services. Having looked at what Hon Mabus has instituted, it is a slick policy and it makes sense. It combines Convalescence Leave, with permissive time, which does not have to be used concurrently over the first year of a child's life which I think will benefit both the service and the service member. We talk about maintaining the military family balance, as well as recruiting more women. This policy among many others he is instituting does that. The man is doing what he sets out to do and from what I can see the vast majority of it is just plain beneficial to the services.

As the USN/USMC are smaller than the Army, it allows things to be test-bedded and vetted for issues, and for things to be tweaked for the larger service.

I have a feeling this will be a running trend in the future. The smaller services will "try" things, and then the larger ones will adopt them as they work. That's just good policy.

Personally I believe that the use of a sabbatical is in order here. This allows family decisions such as having a new addition to be balanced with career decisions. It also allows the parent to decide how long they will dedicate their time. A counter argument may come into play when discussing the fact that when you leave on a sabbatical, you don't get paid. We all know that having children has its costs and this should also come into factoring the decision to expand said family.
I am thinking about this in a logical way while also knowing that my children were both 'surprises' (although my wife was a stay at home mom for the first 12 years)
Many European companies give a full year off with pay for maternity leave. Is that what we are moving towards? Will that affect readiness or promotion? At what point does it become non-rated time?

yes, I think it would be a good idea.