Here's some speculation not based in any fact. Perhaps they are not merely porting it, but at the same time they are trying to get rid of those few code issues that show up in the PC version. IF they are fixing and porting then you could expect that it would take quite some time. Any improvements they make to the old code could then be folded back into the PC version. Pure speculation, but I like it. 

Image Line started on their Mac version long before Sonar and it's not finished.  Porting PC to Mac may be harder than anyone thought.  Windows and Mac are evolving systems.  While Windows has backwards compatibility maybe it is not so much for a Mac.  I still use M-Audio gear bought shortly after the turn of the century and they work. Mac user now have doorstops. (FW 410). 
 
 I probably wouldn't want to use an app that hasn't matured on a platform.  If Logic were available to Windows I'd wait a long time before buying it.

ampfixer
Here's some speculation not based in any fact. Perhaps they are not merely porting it, but at the same time they are trying to get rid of those few code issues that show up in the PC version. IF they are fixing and porting then you could expect that it would take quite some time. Any improvements they make to the old code could then be folded back into the PC version. Pure speculation, but I like it. 

 
that's a kin to something i have thought, that perhaps a side effect of doing a mac version would possibly aid some of the long standing issues and annoyances that people have in the pc version, big or small, and freshen things up a bit. sort of might fit in with the comment that one cakewalk dude made some time back about 'taking the knife' to sonars core. in my mind it's more than possible that the pc version of sonar could also benefit greatly from the development of a mac version. time will tell.

Pretty sure all those complaining about the possibility of fraud didn't read the ToC. 
I bet there isn't more than a handful of people who bought an entirely new license (ie not currently making music with sonar on Windows) just because of a promise of an alpha some time in the future. Most of the people complaining are just cranks who justify their existence insisting that a company to which they have no personal connection owes them something.
If I had my druthers I'd ban anybody who complains about this again. 
 

gunboatdiplomacy
Pretty sure all those complaining about the possibility of fraud didn't read the ToC. 
I bet there isn't more than a handful of people who bought an entirely new license (ie not currently making music with sonar on Windows) just because of a promise of an alpha some time in the future. Most of the people complaining are just cranks who justify their existence insisting that a company to which they have no personal connection owes them something.
If I had my druthers I'd ban anybody who complains about this again. 
 

I'm not complaining, as I'm a Windows guy through and through, but am still very interested in this subject.  I don't doubt for a second that this would be a HUGE undertaking for CW.
 
I guess from my point of view, Mac support might be seen as necessary to gain industry credibility, as there are still some studios out there that would never let a PC darken their door (or should I say, darken their DAW) :)

mettelus
Payment (specifically) for expected product not received falls into levels of fraud. First point is getting money back, so if anyone falls into that category above, check out FTC.gov/complaint

Anyone who bought SONAR based on a statement that an alpha version would be released "to test the waters" seriously needs to re-think how they purchase software.

But wasn't the lifetime updates offer for a limited time?

Just saw this on the Facebook Cakewalk Users Group
Written by a Cakewalk employee but the details didn't copy over here, I guess because it's a closed group.

From Wednesday 8th March 2017.
"We've been slow to follow-up, but we'll have an update on that in the next several weeks."
In response to;
"Hey cakewalk, where can i get a mac version of Sonar?"

gunboatdiplomacy
Pretty sure all those complaining about the possibility of fraud didn't read the ToC. 
I bet there isn't more than a handful of people who bought an entirely new license (ie not currently making music with sonar on Windows) just because of a promise of an alpha some time in the future. Most of the people complaining are just cranks who justify their existence insisting that a company to which they have no personal connection owes them something.
If I had my druthers I'd ban anybody who complains about this again. 
 

username checks out

BRuys
I guess from my point of view, Mac support might be seen as necessary to gain industry credibility, as there are still some studios out there that would never let a PC darken their door (or should I say, darken their DAW) :)

An Apple computer is just normal PC, assembled by one particular company with name "Apple". From hardware point of view, it is not far away from Dell, Acer, StudioCat, etc... "Mac" vs "PC" as PPC vs Intel is in history. Intel won the battle. I got an impression OS X (10) distance to OS 9 is at least as big as PPC -> Intel / OS X -> Windows. I mean Windows XP -> Windows 10 was evaluational, OS 9 -> OS X was a revolution.
 
Apply has managed to develop and keep distinct OS. All other (Sun, Dec, IBM) either disappear or gave up. The trick was to concentrate on "front end" only (the graphic part) and take as much as possible from what exists and is proved by time (BSD). The marketing was good, they have "discovered" interesting tendency in the current world customers preferences: people are ready to pay a lot for an "exclusive quality" as long as they believe it can be called so; durability and backward compatibility have almost no weight;  it is simpler to explain people what they "should do" than try to find and apply what is the best for them. Awesome success story, at least so far...
 
I understand that as the result some people are attracted for life to the Apple brand. But that is the same as with Mercedes, Ford, Always +, etc. I mean the question is the Label, much less (if at all) in the content...