  Yes - there are plans to use them for domestic trains. In fact the southernmost one has its own passenger entrance (accessed from the old station platform rather than through the old Eurostar facilities, though it wasn't (yet) in use when I saw it. The 5 platforms may be chopped in half with pointwork to give 8-10 regular length platforms in lieu of the long 5 Eurostar platforms (my theory; nobody seems to have decided yet).