I read your lines twice, and I am still confused. The NightJet 402 from Zurich to Cologne will not serve along the Gotthard route, so I have difficulties understanding why and how you should be impacted by this incident. If there are connecting trains taking you to Zurich, it would be helpful to know your complete itinerary. Unfortunately, you are not providing this information.
As a general saying, the SBB timetable is up-to-date until 01 October. Since 24 August, international trains are again running from Zurich to Italy and v.v., simply needing more time for the Zurich to Chiasso stretch. What concerns the repair work in the Gotthard Base Tunnel, there is great progress with every new day. Consequently, the situation on 22 October will be much better than today and there might be improvements in the situation which are in your favour. There is no need to worry now about an event that will happen in two months.
We can check your situation in more depth if you provide us the complete itinerary.