I first learned about Patri Friedman's Seasteading ideas and the work he has been doing on this via the Russ Roberts econtalk interview. There is now an article with more in the July 2009 Reason.
Seasteading will happen, but we do not know when.
We do know three things. Liberty is a powerful draw, and technology is progressing faster than ever (on the side of seasteading feasibility), and politicians will keep doing what comes naturally, pushing ever more people into the "exit" option (as in Albert Hirschman's Exit, Voice Loyalty).
I do not see any of these three phenomena receding. So seasteading will happen.