There's an Adobe blog post that basically lays out there isn't much growth happening within the Linux desktop market. "So, with Desktop Linux, we see a basically flat growth curve hovering around 1%. And since the release of AIR, we’ve seen only a 0.5% download share for desktop Linux."
With Adobe AIR 2.7, they will make a "Linux porting kit for AIR" available to their Open Screen Project partners, but it isn't the same as a Linux client. Adobe isn't interested in releasing their own Linux client any more due to better growth and opportunities happening for Android and iOS where they can better allocate their developers.
Right now this Linux change is just surrounding AIR, but other Adobe platforms may be affected as well. "This move will allow us to focus our platforms on the future of Linux clients – on mobile devices. Improving performance, expanding capabilities, cross-device compatibility, stability are things we think are necessary to drive the new Linux market." [Note that platforms are indicated and just not a single platform.]