On 13 January 2016, the Committee on Education, Research and Technology Assessment passed a draft bill to amend the Higher Education Statistics Act. The good news is:
Guest auditor statistics will remain part of the higher education statistics and will not be discontinued, as originally planned.

The Federal Working Group on Advanced Scientific Training for Older People (BAG WiWA), together with the board of the German Association for Further Education and Distance Learning (DGWF), had written a protest note to the committee in favour of retaining guest auditor statistics in order to ensure the continued visibility of this further education opportunity in the higher education context.
Especially in view of an ageing and more diverse society, the importance of this type of further education will increase, promoting individual and customised university further education activities over the course of a student's life.

You can find more information on the guest auditor programme here.