It'll be interesting to see how http://uxexchange.com/ affects list activity/discussion types and, possibly, the interaction design etc of ixda.org.
probably the same thing Quora, LinkedIn Discussions, Facebook groups and all the other alternative places to just have a discussion. Pretty much nothing. For whatever reason there appears to be infinite space for all types of discussion forums around UX. UX Exchange has been around for a few months now and I haven't really noticed any changes (yet).