I just want to say that I've found the next sentence on WM UK website:
Для української мови Вікіпедії ласка, відвідайте http://uk.wikipedia.org; для Вікімедіа Україна відвідайте http://ua.wikimedia.org
It would be good to have such messages more often. For example, Serbian Wikipedia should have similar message with redirecting people to Sranan Tongo language (Suriname Creole) [1] Wikipedia edition [2] (visible portion of Serbian Wikipedia visitors are coming from Suriname because of their ISO 3166-1/TLD code).
Maybe we should gather similar cases and ask relevant communities to make such one-sentence guides at their Main Pages.
[1] http://en.wikipedia.org/wiki/Sranan_Tongo [2] http://srn.wikipedia.org/