Today Russia signaled concerns of the large Russian minority in Estonia.
Reuters reported:

Russia signaled concern on Wednesday at Estonia’s treatment of its large ethnic Russian minority, comparing language policy in the Baltic state with what it said was a call in Ukraine to prevent the use of Russian.

Russia has defended its annexation of Ukraine’s Crimea peninsula by arguing it has the right to protect Russian-speakers outside its borders, so the reference to linguistic tensions in another former Soviet republic comes at a highly sensitive moment.

Russia fully supported the protection of the rights of linguistic minorities, a Moscow diplomat told the United Nations Human Rights Council in Geneva, according to a summary of the session issued by the U.N.’s information department.

“Language should not be used to segregate and isolate groups,” the diplomat was reported as saying. Russia was “concerned by steps taken in this regard in Estonia as well as in Ukraine,” the Moscow envoy was said to have added.

Ted Cruz warned about this earlier today.

Today his sights are set on Ukraine, but if he continues undeterred tomorrow it could be Estonia, Latvia, Moldova, Romania, the Czech Republic, or Poland. Meeting his challenge now with strength, not appeasement, would be the best way to ensure that this does not happen, and that we do not squander our hard-won Cold War victory over the Soviets.

http://www.thegatewaypundit.com/2014/03/...-earlier-today/

And, why shouldn't they? Absolutely nothing to stop them and lots to gain.