Due the desired movement of Outsystems into the Enterprise IT world, from my experience, sooner or later, it will be needed a way to easily connect to MQ based ESB's or EAI. It should be a native feature of the Agile platform to have a way to subscribe to a message queue (MSMQ or JMS) and fire an Action or a BPT process whenever a message with certain characteristics arrives to that queue.
It should be analyzed the fact that an ESB or EAI processes thousands of messages per second, so I believe that a tie to the RDBMS might not be a good technical solution.
It should also be possible to write to queues (the idiom should be the same as Webservices).
At least the standard: Point-to-Point, Publish/Subscribe and Broadcast message transmission/reception models should be supported.