It's to bad for us and too bad for the employees but the handwriting was on the wall. The consolidation of the industry around ProTools was the big one. There is only 1 winner in software, the 800 lb gorilla. It was written in the IT bible "Crossing the Chasm" decades ago. Desktops - Windows, Mobile - Apple, free mobile Android, Photoshop, and on and on.
The 800-lb gorilla has market saturation and the revenue to upgrade code cycle after cycle and the revenue to out market competition. Companies like a standard for training and support costs. You can find a ProTools expert in minutes.
There are small fish who compete, usually nimble new companies or the walking dead old timers who won't quit the battlefield. A good example is Google for search and browser beating everyone - Yahoo, Bing, IE.
The beginning of the end was X1. Sonar stumbled badly with X1 which was released in beta. Companies who needed DAW production software didn't wait for the fixes. They moved on as quickly as possible. We stayed because we're stubborn and for other reasons.
It's easier and costs less to be an upstart software developer than to be a veteran with 20 years of code to support. The cost of keeping Sonar alive has to be huge. Cubase is in the same boat but they are backed by a committed owner.
If Sonar was break even, maybe someone like Steinberg/Pioneer will keep it going. As others have said, Gibson's Moody's credit rating is near default. When companies are in trouble, they do desperate things. Any business unit that doesn't create positive cash flow is cut, which is probably why Sonar is closing.
It will be interesting to see if the code lasts. I hope so.