As of now we dont see the online status (Online, Away, etc) of the other person in sametime chat window. The online status (Online, Away, etc) should be visible in the chat window also. The chat window may display a little status icon like in sametime contacts list.
Although i know we can get the status updates in the window, but a icon would be give the current status.
So a little icon would inform us about the online status of the person.