You mean that Putin may wait till situation in Ukraine destabilizes further and move troops in after that?
I mean he won't have to move troops anywhere else unless somebody actually asks him to. And I didn't mean just the Ukraine - however humorous it may seem, other contestable territories holding their own little referendums is entirely possible, even if highly unlikely to succeed.
Even then, Crimea will be enough of a strain on our existing resources as is - we just won't have the infrastructure capacity to outright acquire any more territory. It'll take time and effort to organize things there until they once again run smoothly. Just compensating for the lost electrical power supply is going to be quite the project on its own, with both temporary measures needed
yesterday and the more permanent solutions rerouted from elsewhere. Add on to that economical restructuring to anticipate any further moves by the West (I've already backed up my Steam library in case Valve caves in, so I'm good), and it's pretty clear that any further annexatory movements are not in Russia's - or Putin's - interests in the slightest.
Plus, if anyone's going to move troops into Ukraine now, it'll most likely be NATO. It's more than likely that everyone's already mobilized enough that we won't beat anyone else to the punch in any other destabilizing region.
The only way we'll gain more territory after Crimea, at least in foreseeable future, is if that territory just up and changes flag on its own.