SportCenter's Steve Levy just noted that following a WNBA championship in 2003, the Detroit Shock were poised to become the league's first dynasty before losing in the first round the next two postseasons.

I'm no WNBA historian, but a quick Wikipedia check shows that the first four championships were won by the Houston Comets.  The definition of a sports dynasty is often vague and always debated, but one would think that such a streak might qualify.