You are talking about replacement of the current destroyers, and maybe cruisers by frigates, then, because the current frigates in service are modern (only 3 from before 2002 and one is in the reserve).
I really do not think that the Russian fleet is old. I do not think that ships of the 1980s, in this case destroyers and cruisers, need to be replaced by age, when we see still some ship from 1968 and 1969 in active service. I think that Russia has been decommissioning ships young still to adapt its size but not by age. Russia should have been keeping the most adapted ships of the Sovietic fleet to the current requirements, then, these ships should remain longer when Russia reachs the projected size for its fleet.
The people should not expect a fast retirement of Sovietic ships until the last. Early retirement of ships is a bad business, and only has some sense when they are not needed. And the Russian fleet will reach the balance for its new right size before the sovietic ships to be finished. It means the last Sovietic ships will be needed ships, and as consequence will not be retired early as others. The last Sovietic ships will remain until to complete their entire life cycle.
If there are still early retirements of some destroyers and cruisers, is because the retired ships are not considered necessary. It means they will not be replaced.
If there are not more early retirements is because the current ships are needed, and then would remain until to be old. The ships obviously would be replaced then.
Russia seems to be decommissioning still young ships, or at least did it until very recently (at least until 2014). Until now the reason of the new ships has not been to replace the retired ships, but to cover new needs and to develop modern ships, opening new lines of production of modern ships. Despite the lack of production of new ships Russia is keeps living the research, development and production lines of new ships. It is likely that Russia did what you said at this level, but Russia has not a need to keep what you said for the replacement of other ships in the short-mid term.
I do not expect Russia expanding its fleet significantly in the short-mid term. Also I do not expect Russia producing many ships in the short-mid term. It would make the recent decommission of young ships a big mistake, proving a bad calculus of the right size for the Russian fleet in recent years. I would expect a Russian fleet with stable number of ships in at least one decade, maybe two, after reaching the wanted size. I would expect the calculus of the size of the fleet in the previous years to be right.