At a press-conference held in New York as part of the NPT review conference activities, Russian officials said that Russia is ready to reduce its nuclear forces to 1500 warheads. Although hardly a firm commitment, it is a good sign that deeper nuclear reductions are possible. A hardly surprising one, though.
The first time Russia officially committed itself to reducing its arsenal to 1500 nuclear warheads was the November 13, 2000 statement by president Putin (which left largely unnoticed because everybody was watching the Florida vote recount). In 2002, Russia agreed to the 1700-2200 ceiling in the Moscow Treaty, but only to avoid embarrassment of a too wide a spread in the treaty numbers - it wanted a lower number, but the United States said it won't go lower than 2200 in any event.
If we look at the current trends, 1500 warheads is what Russia can realistically have in about ten years - 150 land-based missiles with 600 warheads, six submarines with 400 or so warheads on their missiles, and about 500 nuclear cruise missiles carried by strategic bombers.
To go below these numbers would mean taking some fairly radical steps - scrapping more R-36M2/SS-18 missiles, scaling down the submarine force, or converting more bombers to conventional missions. But none of this is impossible and in the long run would certainly prove healthy for the strategic forces. Not to mention that it would make us a bit safer.