I think there is a lot more to this than meets the eye.  There are the emerging rules (https://www.acq.osd.mil/ae/assets/docs/USA002825-19%20Signed%20Memo%20(Software).pdf) that allow for a lot more flexibility than the old rules, but it requires a lot of preparation.  I still haven't thoroughly digested them, but one of interest is that the new rules don't require software upgrades to go back through JCIDS if the MDA agrees. 

There are also other indications that the software may soon get its own color-of-money.  Currently, the color of money issue is only for select pilot programs.    As it existed before, if software that is in sustainment needed an upgrade, then the program had to go through a decision process that identified what the appropriate color was to be.  Depending on the answers, there was the possibility of using R&D or O&M.  Generally you can use O&M as long as there were no changes to the operational requirements and did not need to go through OT/DT.  It is my understanding that cyber requirements are considered to be performance features and not operational requirements.  The new interim policy may make that moot issue anyway.

Coupled to these two changes is the idea that software is going to become "eternal".  The concept of development and sustainment are being phased out and replaced by a variable pace.  It allows the possibility for a dial-up or dial-down pace of work.  There are some big contracting implications to that and I don't know what those are.