There are two problems, and the bit of the article there is slightly misleading: While most of eastern Ukraine speaks Russian, a good portion of Western Ukraine does too (70% of Kyiv, Yushchenko's de facto home base, speaks Russian), and there is little difference between the Russian and Ukrainian languages, anyway. The language difference line is very misleading and not, frankly, a good argument for splitting the country.
Also, only three territories have as yet even uttered the possibility of secession, and only two of those have proposed any action thereof, both being generally divisive in the populace. I don't doubt that Kuchma and Yanukovich could rally up a bucket of support for a split referendum, but as of right now, the rabid desire necessary simply isn't there...