Yeah, cheaper phones don't get as much attention and probably won't get Android OS updates. So if you buy some cheap $200 (full price) Android phone with 4.1 on it, you are probably stuck with that.
But some good news is fragmentation sounds like it's less of an issue these days than it has been in the past. More Google apps and features are separated from the OS. So even if you don't have the latest version of Android you'll have the latest Gmail, YouTube, even keyboard. Also just this past Google IO a big new thing they talked about was new Service APIs that update automatically from Google Play and allow older versions of Android to automatically support new app features that current versions of Android have without needing an OS update.
So while the OS might be a bit behind, you should be able to run most of the newest apps and enjoy all the new features in them, is my interpretation of this announcement.