Hey Greg! Good coverage of real-time. I look forward all of this stuff in the near future.
These tools will need a strong foundation for developers to build on. In my view, the future won't be achievable without pushing new content to subscribers (aka fat pinging) instead of the ping/poll model. This is why I'm an advocate of PubSubHubbub.
I go into the details in this investigation of ping versus push:
Please check it out!