I think the test will come when, or indeed if, UX Exchange migrates to SE 2.0.
I think that there are two possibilities (NOTE I'm not trying to put words into people's mouths or tell anyone what to do):
a) They decide not to migrate but just direct traffic to this site. This might then have the effect of shifting the focus of this site slightly - which wouldn't necessarily be a bad thing but would have to be treated with caution.
b) They migrate to a new SE 2.0 site at which point there might be a battle for visitors - the outcome of which could be that neither site survives.
There are other sites that have significant overlap with each other so seeing how they fare may well have some bearing on what happens.