Moving to 3.0. The Core Spring Framework is adding Async support for Spring 3.2 . Furthermore, they are exploring ways to best support Websockets moving forward 
As the Spring Integration team would like to align its Websockets/Async support with the Core Spring as much as possible, we will move this adapter to Spring Integration 3.0. In the mean-time, once
INT-1958 is fixed, the Atmosphere based adapters will be moved to the Spring Integration Extensions project.