Well, probably somebody does not understand about all the present Russian achievements, but before any discussion it is necessary to imagine who researches and does all these super-new, super-terrible and super-horrible missiles? My exact answer - nobody. In Russia there are no specialists now, because there is no education, no science and almost no production. Therefore, I can tell you exactly - there will be neither C-500, nor C-600, nor C-700 and even nor C-1000. It could be just very old C-300 and their modification C-400.
Who does not trust this, my short info. In the period 2001-2012, my small company rented an area on former Almaz-Antey territory, near their design bureau, the main developer of all the Russian main anti-aircraft systems (in 1950th in this place the Russian developments of German Wasserfale missile made with the help of captive German engineers). But in that time, I mean 2001-2012, in their design bureau, where of 90% area was rented out to business, only the old people were left, and no new research was done. The latest part of their research was remaking the old S-300 into the new S-300 missile launchers by throwing out the multiple old lamp electric cabinets (the best Soviet electronics!), replacing them to small boxes with the cheapest Chinese chips (which I saw myself in the one rest their workshop). Now they are not even able to do that, because this territory was completely closed as design bureau and factory in 2014 and transferred to another factory in Moscow (Lianozovo).