The ability to deploy a .sar exists in AS7. However, the ability to configure a datasource within a deployment doesn't currently exist. See this http://community.jboss.org/thread/164554?tstart=0 for a discussion about this.
Thanks, that links to basically the same challenges (and they added JMS which I also do on one application through SAR).
However, there seems to be lack of (clear/suported) direction/support towards a 'migration' approach for people who do follow the SAR approach to manage resource configuration seperate from BOTH the application and the server (where a single server is likely to support multiple apps/configurations and rather than having a single large configuration for ALL applications to allow each application SAR to configure itself and adjust/mature without impacting other running applications).
The .cli approach mentioned sounds good in theory, but leaves current SAR users fumbling.