There is not much more what I can add to what is already said, so I give my personal view on this case.
First of all - A lot of people raged when Sonar went from 8.5 to the "X" series. Personally I think they did a really good move with that. It was all about attracting "new blood", and that was really needed for Cakewalk to survive.
Secondly (and that's again a personal opinion) - I think dropping Project 5 was not an very clever idea. It was a program with a lot of potential. Yes - there was Ableton Live too, but there WAS room for an contender. Just look at Bitwig, and you get what I mean.
Later they tried the above again with the matrix view, but sadly after the introduction it was never developed any further. It was some halfway development, that lead nowhere at the end. And that's a shame, because it has a huge potential to draw in that badly needed "new blood".
This was symptomatic for the direction Sonar was heading. I have the feeling Cakewalk was aiming at the more "professional" section of the market. I think that was a big mistake, because that "top of the market" was already occupied by some big brands. Sonar simply had no chance to wriggle itself into that high end of the market.
A lot of us (luckily not all of us) look down on what's called "bedroom producers". Unfortunately for them that's where the money is at this moment. And those people are intensive users of MIDI, samples and loops. Like it or not - If Cakewalk had developed Project 5 further, and gave it the same attention and "outfit" as they gave the Sonar series, they would have a potential winner on their hands now. They got a second chance with the matrix in Sonar, but, frankly said, they blew it. And by that they just lost the chance to draw in that group of new users.
All what I said here is nothing new. I have been saying that from the moment they dropped Project 5. I was always an fierce promoter of the "X" direction Sonar was taking, and was very happy when the matrix was introduced. Over the years I got less enthusiastic, because the development in the direction I thought was needed was stagnating. For me the tipping point was when Sonar's MIDI got lagging behind what other programs (like Cubase) where offering me. Add to that the increased yearly cost, and the battle was in humble opinion "lost".
It's sad Sonar ended this way, but it does not surprise me. They had their chances, but kept primarily targeting the wrong market and at the end failed.