CM devs are consumers first. What this means is that they do not divide up devices among other developers, or assign devices like one would at a job. Developers work in their spare time without monetary compensation. Because of this, the developers are free to work on any device they choose to purchase.
Now, what does this mean to you? First off, requesting anywhere in the CM forum, the CM Blog, or the Facebook/Google+/Twitter accounts for device XX to be supported is probably a waste of your time and anybody who reads said request. CyanogenMod does not work on device requests as there is no guaranteeing that a current CM maintainer is even interested in the device. Additionally, its not as simple as 'porting' code, the device trees must be coded from scratch and made to work with the AOSP sourced code and CM enhancements. This takes a large amount of time and effort, especially when the device's OEM fails to release the latest version of Android for it. Second, in hoping a worthy developer sees the post and decides to take up the project... well, that is probably just wishful thinking. Many developers do not like interacting with end users (too much finger pointing between both devs and users or anger directed at the devs for something working other than how the user expects - it happens far too often); because of that, many developers don't frequent the forum (or if they do, they only view the forums for the devices they maintain). The best way to get a device official support is not requesting it from the CM team, but learning how to do it yourself or encouraging a maintainer of an unofficial build to submit their code for review.
So, Cyanogenmod devs will support what strikes their fancy. And if they are no longer interested in a device, it won't be supported any longer. Now if they get financing, maybe this will change as most consumers want some stability and continued support. It is one of the things that could differentiate itself from the phone makers... if they care to. If not, in this regard they won't be any different. And it would be a shame since it is nice to get rid of bloatware.
The vast majority of people will not port their own devices. They either don't have the time or the technical know-how or nether. I will use the stock OS if it isn't available as a stable CM. In fact I do with my P600 Samsung Note. But even if they did, after reading that sticky from the forum, I am less willing to adopt CM and choose to just root the device instead.