For a start I don't see that ever happening, the F-35A acquisition program for the RAAF is way too far down the track to ever imagine that the Government would do a 'U turn' and look at an alternative, why would it? If anything the F-35 program appears to be going along relatively smoothly these days.
A couple of points.
The so called 'Advanced Super Hornet' is just a concept, does not actually exist. Sure Boeing has produced a 'concept' demonstrator, but from what I understand, whilst it might have been an aerodynamic representation of what an ASH might look like, things like the conformal tanks and the weapons pod were not actually real production items, and that of course doesn't include all the avionic and engine upgrades either.
Any nation that puts in an order for the ASH is going to be slugged with all the development costs of turning the 'concept' into reality, and then of course you would potentially end up with an 'orphan' sub-fleet of airframes.
As I've always understood it, the RAAF is going to be in 'lock step' with the USN when it comes to the configuration of the Super Hornet, what they do, we do, makes a ton of sense from a supportability point of view to say the least.
The only way I could ever image the ASH becoming a reality is if the USN decides that 'all' of it Super Hornets are to be upgraded to the standard that Boeing has proposed, and seriously, I can't see that happening.
That's not to say that some 'components' of the proposed ASH might filter through to the USN's fleet of Super Hornets, such as conformal tanks, especially for the Growlers, but again, unless the USN adopts such modifications, then I just can't see that the RAAF would go out on a limb and create it's own small 'sub-class' of Super Hornets.
The other point to be made about your suggestion of '138' ASH, where does all the extra ground and aircrews come from? Where are theses extra airframes going to be based?
And most importantly, how much is it going to cost to provide all that extra manpower and basing?
No, let's just stick with the initial 72 F-35A's and hopefully eventually approx. 100 F-35A's!!!