Could the note be dynamic, with three options? Read the current version (it’s stored as a variable somewhere), then add three options/checkboxes:
– automatically update to 5.6 when it comes out.
– automatically update to 5.5.4 when it comes out.
– remember these settings after the next update.

And a link to a wordpress.org post explaining the differences more fully.
And only available to Admin users, of course.