re: "does this feature got enhancement in jboss later version?"
There are two possible answers, in general: (1) for Remoting 2 (AS 4,5,6) and (2) Remoting 3 (AS 7). Unfortunately, I don't know enough about Remoting 3 to answer.
With respect to Remoting 2:
re: "add a default timeout,"
I'm not really sure what you mean. The code itself has a hard coded default timeout of 30 minutes. If you set the "timeout" parameter, that value becomes the timeout value for all invocations.
re: "let user can specify different timeout value in ejb method level"
Remoting 2 is currently in maintenance mode and there will be no new features.