No I think Twitter will be around for awhile. Maybe not for most people but the service was orignally designed to be a way for major corps and pesudo clebs like say John Davidson from 1up and game jouro shit bins(all of them ) to keep in contact with their fanbase without having to add them to their Facebook since FB is suppose to be a closed off social network just for your close friends.
Twitter allows anyone to simply and very non evasivly keep in touch with the people and businesses they care about. Its been a great way to get info out about new products, sales, or just what everyone is into at a time.
Its a fantastic service that will have a long life outside of people who just tweet about their bowel movements.