It's been exactly one year since I looked at the status of the Russian space-based early-warning system. This means that I missed the point when one of the satellites deployed on a highly-elliptical orbit, Cosmos-2469 (37170), stopped operations. The satellite, launched in September 2010, did not perform a regular orbit-keeping maneuver expected in February-March 2013. It has been drifting off the station since then.
Cosmos-2469 was reported to be the last satellite of the 73D6 type deployed on HEO, so no more HEO launches are expected. There are still two working satellites on HEO - Cosmos-2422 (launched in July 2006, it is the oldest early-warning satellite in orbit) and Cosmos-2446 (launched in December 2008). The is also one geostationary satellite - Cosmos-2479 (this is relatively new - it was launched in March 2012).
Russia has been working on a new space-based early-warning system, EKS, but it's not clear how long this development will take. At some point it was expected that the flight test of the EKS satellites will begin in 2009, then it changed to 2011-2012. In 2011 the new system was a subject of a court case and it looks like it won't be ready for some time. Meanwhile, in 2012 Russia opened a new early-warning control center at Komsomolsk-on Amur, presumably to support operations of the new system.