I've booked next year's Onur flights again through Aegean for the third year running and have to say am not concerned. I got good prices because I booked early and fully appreciate that they are basic flights.
Am a great believer in "what will be will be" and am not concerned in the least about Aegean or Onur going bust - they are incomparible to Goldtrail, Kiss etc and I book with them because I consider them to be reliable with flights at a good price provided I book them early enough
As an OP has previously said, speculation helps no-one especially in these times