It has never been the case that all galaxies show evidence for dark
matter halos (see http://nedwww.ipac.caltech.edu/level5/March01/Battaner/).
The point is that the observed anomalous rotation curves of galaxies
are practically always based on gas velocities which can be very
different from the velocities of stars ( see my webpage
http://www.physicsmyths.org.uk/darkmatter.htm for an alternative
interpretation of the constant velocity curves in this sense).