Will Clearing Houses Overtake Exchanges in Economic Importance?

All derivative exchanges and most stock exchanges have related clearing houses, often separate institutions. Clearing houses themselves are looking to provide clearing services to the OTC markets which are now many times larger than the related formal exchange markets, where they exist. Exchanges have responded to the challenge and launched OTC type products, but with limited success. In this scenario what will be the future role and structure of clearing houses? Can they successfully serve both types of market and, perhaps, become structurally independent of each?