Just in February alone Russia committed, despite the sad economy, to continue heavily investing in new advanced weapon systems, including nuclear missiles. The United States has made no such move.
Statements by the Russian leadership echo the sentiment that they are continuing to modernize. Russia has come out with the Topol-M, and are working on the missile you describe. The United States on the other hand has done nothing.
February of this year they pledged another $36 billion. Putin stated "It's expensive, it's very expensive, but there is no other way. We will develop and modernize our strategic deterrent forces."
My point is that Russia is making strides at upgrades and the US is letting its arsenal atrophy.
I do not lament the lack of parity. I do not even think parity is all that important, which is why I feel that the United States should not be giving anything to Russia in the name of "arms control." Why should we eliminate weapons needlessly? While parity is not the be all end all, what does matter is making sure we have weapons that work and can eliminate targets. I think right now, we are falling behind in that department.
What I want our nuclear arsenal's role to be is to be able to provide our allies with a credible assurance of our security guarantees, thus preventing proliferation and limiting the amount of fissile material.