I am also tremendously curious as to Putin's geopolitical ambitions. He controls a populace that loves him (Putin has very high approval ratings within Russia, I forget the exact numbers), and huge swaths of land and natural resources. He also has effectively unlimited term length, and controls a propaganda machine so powerful it rivals even that of the United States (/snark). All these factors make for a good recipe for going to war.
So why would he want to go to war? Energy. Currently, the Russian oil industry contributes massively to Russian GDP, as it's a net exporter of oil that has always controlled massive swaths of oil-rich land. BUT, in the past couple years, Shale Gas has risen as a viable alternative energy source. The US has so much shale gas that it will be a net energy exporter by 2020, and natural gas prices in the EU are plummeting because of this. Thus, EU energy companies are turning to natural gas sources -- namely, the US -- for their energy, and reducing their dependence on imported Russian oil.
Putin sees the writing on the wall, and he knows that one of Russia's primary income sources is dwindling, as is his stack of bargaining chips along with it. He needs to find a replacement for this income, fast.
According to Wikipedia [1], Ukraine has the 3rd most known Shale deposits of any country. I suspect it's no coincidence that Putin is charging into Ukraine, a country with a promising energy future, at a time when demand for his oil reserves is dwindling.
If I'm correct, and Putin's ultimate motive is the shale gas reserves in Ukraine, this is at least encouraging because it means he will likely stop after taking Ukraine. That may seem bad, but you can't really fault him for that logic, and a lot of Ukrainians seem to support Putin, so it doesn't seem like something the US should put too much effort into stopping.
There are a lot of massive geopolitical shifts happening in the next decade. The US becoming a net energy exporter will have effects on the Middle East, Russia, and other BRICS. Simultaneously, the BRIC countries are opening their own IMF competitor to reduce their dependence on the Petrodollar. And while all this is happening, China is building up its military, Russia is isolating itself, and the US is pumping fodder after fodder into its anti-BRIC propaganda machine.
The next decade looks like one that will be very unstable, and I suspect it will mark the beginning of the next major war. Scary time.
[1] http://en.m.wikipedia.org/wiki/Shale_gas_by_country