Actually right now everyting is quite fluent and non-deterministic for the first time in a decade, so fun times.

Last Duma (Russian Parlament) vote was massively rigged (that's 4 years ago), but still the govenment party (United Russia) had like 50% of the votes, but they got about 70% due to massive vote rigging. This time around with about the same amount of rigging they got 50%. So a lot of people who where saying that the vote was rigged did nothing as anyway they were the winners :) This time they are the minority with a real share of votes about 30%. So the first factor is that there is a subset of people that see they are not only being fooled but being fooled by someone who is now in minority.
As a side thought even without the rigging the parliament could be VERY controlable as all the major parties (communists to a somewhat lesser degree) have built quite close relationship with the current leadership of the country.

The second factor is that the people that go out to the streets of Moscow and other cities are mostly middle-class, educated specialists (I saw some poll results about the 24 December protests by a respected agency with the numbers of about 65% having a degrgee and about 7% having two), so we see a lot of people who have never been into protests but are just quite fed up with what they see around and with the last news about the president-PM swap they know nothing will change for at least a decade. And taking into account that the majority of that people travel to Europe or other parts of the world and see how you really can live better with the same GDP per capita they really want some thing to change for better.
Another point is that 50% for United Russia in Moscow is really really stupid, with real support figures in 20-30% ballpark. I mean WTF?

What is happening now is that the protests while quite small by the 89-90 standarts are still by far the largest protests during Putin time (About 50-70 thousands last time in Moscow). The most interesting stuff will be happening during the March presidential elections as the Putin rating have plumetted below the treshhold that allows him to win outright without a second round (he needs more than 50% and has less than 40%) and going into secont round will be a HUGE hit to the image he tries to show.

So actually noone knows what will happen, except that if we do nothing than nothing will happen and we will have a national leader for life.