Donbass did a Crimea style referendum in 2014; Putin declined to acknowledge it at the time as he just yoinked Crimea from the hands of the Ukrainan govt. who were reeling from the Revolution of Dignity.
There has been fighting continuously since 2014 between the Russian backed separatists and the Ukrainian armed forces; the decision by Putin yesterday to acknowledge the sovereignty of the Donbas region and subsequently their referendum to join Russia allowed him to send in peace keeping forces to finally end the conflict.
Ukraine may push back, but only to save face.
I doubt it will escalate; despite what the WEF will lead you to believe.