Divinity: Original SIn can be played in czech language.

Here: http://www.divinityoriginalsin.com/news.php

is written this:
What languages will be supported in the first release?
English, French, Italian, German, Spanish, Russian, Polish. Voiceover will be available in English only.


Does it mean that czech will be no longer available?

It means it will not be available at release. Other localizations may be released later, but I don't know if that is currently the plan for Czech, or if so, how much of a delay there may be.