I think
Onur Air (OHY) will be fine as they have many other tour operators that charter them and also sizeable domestic scheduled sperations in Turkey.
As for
Turkuaz Airlines (TRK) I would worry, they are a lot smaller and most (if not all) of their UK flights were for Goldtrail. They still have German, Dutch and Belgain tour operators that charter them though and a few Turkish charter operations...
As for
Saga Airlines (SGX)
, again they are also a worry! A small team and fleet, although they also do aircraft leasing for Turkish Airlines and others. The majority (but by no means all) of their UK flights were for Goldtrail, although I think Kiss Flights chartered them as well.
What we need is another firm to step in and replace the gap in capacity that Goldtrail has left. Hopefully supporting these airlines and the hotels..