Beware of Wikipedia. It can be misleading and is often plain wrong. Most universities in examining students will now mark you down should you quote wikipedia (as I have found out to my great cost on several occasions).
So in this case the space time volume of the non-observable universe is expanding, but in fact the light cone of the observable universe is contracting assuming you adopt the standard model of cosmology.
Application of Hubbles so called law to the universe is not simple. Many misconceptions were spelled out by Tamara Davis and Charlie Lineweaver at
http://msowww.anu.edu.au/~charley/pa...neweaver04.pdf
Standard redshift theory is not only rejected by some "folk", but also by many cosmologists, although it is fair to say that the majority accept the implication in greater or lesser degree. At base however, this is simply a theory which is "believed" as there is no way we can travel to other galaxies to test variance in physical parameters of the influence on redshift measurements from other effects. The main plank on which cosmologists base their assumptions is simply consistency of measurement over several disiplines together with occams razor i.e. the simples solution is usually the best.
Personally I find the current cosmological model compelling but should another arise which negates standard redshift assumptions I would neither be shocked or surprised.