Unless something drastic changed (or I'm utterly misinformed) you could run your own server - and you'd split the network. The explanation was, as far as I recall, that there's no easy way to route things if all you got is a mobile number as an identifier (So .. on what server is that client? A JID has a host, a mobile number doesn't).
To reiterate: You probably could run your own server. In which case you and the 3-5 people you might convince to use that server would share some infrastructure under your control. You would not be able to send a message to the 6th friend that happens to use TextSecure, but _also_ needs to be on the authentic/real network to chat with his family.
Edit: Partially based on https://twitter.com/moxie/status/438049169052155905