So yes, if the plugin behaves according to the VST 2.4 standard, and it is an Instrument or an Effect, then it will work.If your VST is a VST version 2.4 instrument or effect, then YES it will work!
What does not work is VST midi plugins that send midi. However this is just version 1 of VST in Reason. We focused on instruments and effects first.
Because there are thousands of plugins that say they comply with VST 2.4, Propellerhead can't check them all to make sure they really do. Thats also why there is a beta. If you find one that is misbehaving tell propellerhead.
More info around the 11 minutes mark: