Not analytics related, but, won't this break a whole bunch of ORA related stuff?  If I start an open ended problem before this is released to prod, save my answer, and then refresh the page after this code has been deployed... will I still be able to see my saved answer?  I have very little knowledge of that subsystem... but I thought it was using these IDs to link its data back to the LMS data.

I think we also expose this ID to problems in some fashion so that instructors can embed links to surveys etc.  I imagine this change would impact those elements as well.

Assuming the ORA linkage is worked out, the analytics impact isn't huge, but we will have to add some logic to our export scripts that ensures that this new anonymous_student_id table is exported to our partners.  It will add some confusion, but nothing unreasonable IMHO.