The first potential shift is dropping the M-Class name from the range because it just no longer fits within a naming structure that has SUVs and CUVs all starting with G. According to Car and Driver speaking with unnamed Mercedes insiders, when the crossover gets refreshed with updated styling in 2015, it's also getting a new name: GLE-Class. Then, when the Concept Coupe SUV goes into production, it would be called the GLE Coupe.
The rumored changes to the M-Class might be only the beginning, though. Once the GLE falls in place, the future version of the GLK-Class would possibly become the GLC-Class. Just those two revisions would give the Mercedes' mainstream SUV and CUV range a similar hierarchy as its sedans with the GLA-Class, GLC-Class, GLE-Class and GL-Class all having roughly corresponding models, plus the G-Class out on its own as its incomparable self. If it all actually happens, the re-naming should make the lineup easier to understand. Autoblog reached out to Mercedes spokesperson Christian Bokich to confirm all of this, but all he would say is, "I'm afraid that it's too early to tell at this point."