I am sorry but this "take it or leave it" idea to asking Russians to become "Ukrainian or leave" sounds like some kind of a twisted neo-nazi ethnic cleansing idea. It goes beyond the modern European norms of human rights of minorities. And it really cracks me up when Ukrainian or say Estonian nationalists love to say that they share European liberal-democratic values, but are also quick to judge and treat their Russian minority as some kind of "fifth column", people of second rank, while also rehabilitating their nazi-collaborating, Jew-killing nationalist ancestors of WWII era, who were considered traitors under USSR.
And what did Ukraine's Russians do to deserve such "solution"? For one, they're living on their historic homeland of many hundreds years. They're not a "fifth column" like some Russia-haters want to believe. The South East Ukraine was conquered by the Russian empire from Crimean Turks in 18th century, not from Ukrainians (in fact term Ukraine as geographic designation didn't become common until late 19th century). At the time of conquest, it was an empty land as it was the policy of Crimean Turks to keep it empty and use it as free a path to raiding lands in the north for obtaining slaves and loot to be sold into Ottoman Empire. Both Russians and Ukrainians settled it in 18-19th century, and then the Russian Empire and USSR spent a lot of effort on building up and industrializing that area. The area was historically called "New Russia" before the revolution, but by some bizarre twist of history, the early day Soviet Communist, and Lenin in particular, decided to roll former "New Russia" into Ukraine SSR jurisdiction, that that's how it's now part of independent Ukraine.
But anyways, regardless of what the history was, the human rights and the right to self determination should always be respected. So in particular Ukraine's minorities, or any other country, should have a right to cultural autonomy if not outright political one.