I wouldn't say the Napoleonic Prussian reserves and Russian grenadiers have vanished forever : it seems more likely their release has been postponed to an unspecified date. The greens are done, so it's just a matter of squeezing them into the production process according to priority. AWI Continentals and militia are also rumoured to be in the pipeline along with the ACW federal infantry set, and Alan Perry has very indirectly hinted that there may be a plastic 1807-1812 FRench infantry set at some point in the future.
As it is, I wouldn't be surprised if Perry Mins released the WW2 Desert sets for Salute after but I'm not privy to any inside information so may well be wrong here.