Which, as the direct quote from Steve Jobs I included above, was explicitly Jobs' long term plan. So how does that make him the Mac's most ardent defender when his primary focus was on "the next great thing"? That is the disconnect from reality.
In in this universe. Your alternative universe is where Jobs isn't primarily weighting the "next great thing" and keeping the Mac as the central focus of Apple for the long term.
An example of "milking it for all it is worth" only reinforces the quote I cited above. The issue is whether you have some example other than the plan that Jobs laid out. Jobs' Apple works with 5 year plan outlines for products. The stuff in 2013-2015 still had some inputs (or deallocation of resources; say no ) from Jobs on them.
Besides, the current MBA is not filling the same role as the 2008 MBA. The MBA of 2008 was a slightly upscale/upmarket system (price premium on thinnest/lightest). Namely, the MBA and MacBook have swapped places. The purpose the Macbook name served in 2008 is exactly the role that the MBA 2015 is playing ( entry level price point). Same is true for the Macbook of 2015. It is now in the same role as the MBA was in 2008 ( maximum lightest, thinnest system from Apple. )
Jobs might have killed off the MBA 11" and pushed the MBA 13" into that price point. But he still would need an "entry level" computer. And the latest , greatest tech isn't going to work with the "required" profit margins ( also a constraint Jobs was fully on board with). Or perhaps Jobs would have just swapped the names.
That would be another alternative universe where IBM was still in the consumer computer business. They aren't. In this reality, IBM is mostly a services company now. Any computer hardware is corporate data center types of offerings. They don't need OS X. OS X is largely only valuable to Apple. There is nobody else that is going to make that work. OS X decoupled from the hardware is a lost cause. OS X doesn't easily decouple from iOS ( and tvOS) either. The cost structure for maintaining some of the shared infrastructure is paid for by the much larger iOS market. Pull that money and talent out of the R&D and have a bigger issue. Dell , HP , Lenovo ... they are all trending water as PC vendors. ( Dell is busy trying to consume EMC to remain viable, HP just got spun out and needs to find something else long term, Lenovo without huge China growth has major problems. ..... etc. etc. )
Apple is still pulling folks out of the Window soup at a rate that is quite profitable. There is nobody who has the cash to pay what Apple should charge to sell off OS X when OS X is still very substantially profitable. Try buying Windows off of Microsoft.