The way I see it: as the rate of profit falls, these groups are proletarianized as finance and monopoly capital tries to pad their margins to compensate. As material conditions change, so do class interests and relationships.
The importance of class relationships under particular material conditions is exemplified by the PRC's flag: 5 stars. 4 for the peasantry, proletariat, petite bourgeoisie, and national bourgeoisie. One large star for the Communist Party that united them.