Well, I am generally of the persuasion that given the current state of most Bitcoin exchange APIs, Messaging protocols, etc., it'll be a long time before there is enough genuine incentive for exchanges to offer truly 'real-time' trading protocols.

Take BTC-E which runs a Metatrader server (and regardless of what you think of MT, it's still much snappier than the majority of the BTC Exchanges out there).

Given the majority of order-flow I speculate is still retail, there is little incentive for exchanges to build out algo-oriented communications protocols when the majority of your customers use the website to enter orders.

In short, I don't see 'Bitcoin Exchanges' pushing order messaging as it relates to trading 'forward', though there are some novel approaches to settlement (blockchain) and using multi-sig liquidity verification. At the end of the day if your customer is institutional they'll demand a variety of protocols - if your customer is retail, they probably don't care that much.