If your line of thinking is correct then Twitter will need to make a play for a service to capture the full landscape of posting tools. I personally use Tweetdeck but it is risky to have multiple accounts ie: Chrysler or Secret Service. Services like Tap11, Radian6 and CoTweet have already been snapped up. I suspect more big companies and agencies are going to move away from a 'client' and move to a service model that can meet their needs. If there is fear about changes Twitter may do to the API it will come from impacts to those services, at least for the big companies.