The extension isn't for the MA5616, it's holding blocks for extra tie pairs. Only changes to the MA5616 are software to add support for 48 port line cards and the cards and connectors themselves
If you would care to read what I typed, in context with the other material that was then currently available, you will see I did not express what you are now implying in your latest posting. Your first sentence, above, is -- er -- mischievous.
You should also be aware that there is space in the cabinet "holding frame", available for the insertion of an expansion card-cage, for if/when a vectoring engine is installed.