In South Ossetia and Abkhazia, Russia at least had the excuse that there had been vicious ethnic warfare, making Russian intervention on "humanitarian" grounds more plausible. (Of course, Putin's main motivation for the 2008 South Ossetia War was to punish Georgia for drawing close to NATO).
Putin probably hoped that violence would break out in Ukraine between pro-Western and pro-Russian factions, giving an excuse for the Russian army to intervene to preserve "stability" and the human rights of ethnic Russians. Unfortunately, not enough real anarchy ensued and so Putin was forced to manufacture a crisis using fake "self-defence forces" and a puppet Crimean leader, Aksyonov.
The fate of the autonomous republics
South Ossetia and Abkhazia currently exist in a legal limbo, recognised only by Russia and a handful of other states.
As far as I can gather, Abkhazia would rather be an independent state in its own right. Being de facto part of Russia is no more than second-best; the fear of a return to Georgian rule is what drives it to prefer Moscow.
South Ossetia really would like to become part of the Russian Federation and join up with its kinsmen and women in the Russian Republic of North Ossetia-Alania on the other side of the Caucasus. Nevertheless, Russia is unlikely to give this the go-ahead for fear of angering the other, already restive republics of the North Caucasus. These republics are predominantly Muslim and favouring the Christian Ossetians (as the Russian Empire did historically) would fuel resentment. Such friction led to a war between North Ossetia and neighbouring Ingushetia (the Prigorodny Conflict) in 1992. Adding South Ossetia would further unbalance an already unbalanced region which Russia struggles to control. The expense of "feeding more Caucasians" might also be unpopular with Russian nationalists.
Crimea is different. Until 1954, it was even part of Russia proper. It has a majority of real, ethnic Russians, not Caucasians who have been Russianised by handing out passports. Therefore it is possible Crimea will be the first neighbouring region that Russia fully absorbs into itself. However, we are not there yet. So far, the Ukrainians have been remarkably restrained, but a shooting war might still break out leading to a fratricidal conflict between East Slavs. The move will also be opposed worldwide, barring a few Russian allies like Syria and a handful of tinpot states like Tuvalu and Nauru who are willing to prostitute their UN votes for Russian money. It will inspire fear in neighbouring states with large ethnic Russian populations (Latvia and Estonia will be glad they have joined NATO). China's reaction is difficult to gauge. In recent years, China and Russia have stood shoulder to shoulder in many UN Security Council votes, but this has mainly been because they have both taken a line in favour of non-intervention in other states. Russia has now broken rank, so China may stay neutral. There is also the issue of the Crimean Tatars - and I might look into that at a later date.