The Thameslink website says
The consultation launched on Thursday 15 September and closes at 17:00 on Thursday 8 December 2016.Govia Thameslink Railway (GTR) has launched an extensive consultation which sets out proposed changes to the timetable which will be operated by GTR in 2018 following completion of the Thameslink Programme.
When the programme completes in 2018, it will transform north-south travel through London; journeys will be improved with trains every two to three minutes through central London at peak times. Improved connections will give you better travel options to more destinations than ever before, modern track will make your journeys more reliable and new trains will provide additional capacity. This will be the biggest timetable change on the routes affected in a generation. We are therefore seeking feedback from any interested parties who may be affected by the proposed changes to help shape the new patterns of service.
This consultation will be the earliest a train operator has released proposals in advance of the planned changes allowing sufficient time for meaningful and on-going engagement.
Please download the document with all the detailsTimetable Consultation document
Please download the information sheets with a summary of proposed changes by route:Great Northern Metro
Great Northern Mainline
Central London to Bedford
Southern Metro, Wimbledon Loop and West London Line
Brighton Mainline, Arun Valley, West and East Coastway
Redhill and Oxted