Hi Mike.
Sorry for the slow response.  I was checking the v12 functionality that I'm less familiar with.

Unfortunately the short answer is no.  The link between competency and learning plans is not dynamic so is not aware of changes that may occur to competency frameworks linked to a learning plan.

To respond to your question regarding assignment of competency in v13.
In 13 we have made a number of changes.  One of the more significant ones is to remove the hard relationship between competency and a learning plan. 
We have moved achievement away from learning plans and onto competency itself.  This gives a much finer grained control over how a competency or a competency hierarchy can be achieved.  Competency achievement can now be a combination of child competencies, and/or learning.  User can now manage their achievement directly from the competency feature rather than via a learning plan.

Competency assignment in v13 also includes bulk assignment.  So the process of adding a new competency to a framework and then assigning that new competency to users is easier in 13.

Competency assignment in v13 however is not dynamic, so v13 does not deliver an automated solution to your requirement to draw new competencies into an existing learning plan.  

This article details what is available in 13. https://help.totaralearning.com/display/TH13/Competencies.