A few reasons why the Sea Kings might still be slated for decommissioning without the MRH 90's having been stood up come to mind. IIRC the Sea Kings first began to enter RAN service in the early 1970's. This means that the aircraft are nearing forty years old. This means that more (and more expensive) maintenance is required to keep them in flying condition, and there is also the increased chance of a particular Sea King being down for maintenance and repair. Also, the Sea King AFAIK can only operate from HMAS Success and the current RAN amphibs. Given that HMAS Tobruk and HMAS Kanimbla are both kept 'close to home' due to potential issues with availability... There are not many platforms left in RAN service for the Sea Kings to operate from, nevermind the potential need to have several aboard ship in order to ensure that at least one Sea King is available for taskings when required.
Also worth noting, there is a significant difference between Should be kept in service, Could be kept in service... While the RAN could find such capabilities are the Sea Kings provide, when operating at least, still useful. That does not mean that the Sea Kings could reasonably be kept in service.
-Cheers
Abraham has covered a number of these points in another post, but here's my 2 cents worth.
Yes the Sea Kings are old airframes, but since the problems a number of years ago, I understood that their maintenance standard was quiet high these days.
Two interesting items on the navy.gov.au site:
Rescue on Lord Howe Island (18 May):
Rescue of injured climber on Lord Howe Island by Navy helicopter - Royal Australian Navy
Two Sea Kings flew 700kms, did the job and flew back, not bad for a couple of "old" helicopters.
Preserving the Sea Kings (9 June):
Preserving our Sea King Helicopters - Royal Australian Navy
The article states they WILL be withdrawn in December this year.
My point about keeping them in services longer, or maybe at least not disposing them, till a clear know date for the MRH90's, I think, is valid.
If you look at what has happened over the last few years the current helicopter fleets in the ADF must be pretty stretched.
11 Seasprites handed back, 25 hueys retired from the gunship and utility roles.
The MRH90's are running well behind, the Tigers arnt there yet either, the Chinook's are busy, and a recent loss too will be a strain.
So that basically leaves, come the end of the year, 16 Seahawks and the 34 Blackhawks to do all the roles they currently have to do.
So if there is an emergency during next year, civil or military, I think the Navy and ADF generally could be stretched for utility helicopters.
One last point, maybe with the purchase of the 24 MH60R's, we should also think of getting 6 MH60S's for the navy to cover the utility role.
Very similar aircraft and possibly a lot easier to support for the Navy, and both are in service with the USN.
And let the Army keep the MRH90's.