Yeah, Sorbian language is of great importance for all Slavs. I wish there would be sometime strong and independent from Germany Lusatia, where Sorbian language as one of the most archaic and therefore valuable Slavic languages would be spoken without all this German pronunciation. I am not an expert in West Slavic languages, but what I mentioned is the German "r" for instance in the examples above which falls on my ear disagreeably. Here is one video from Lower Lusatia, where one can hear Sorbian language spoken by the old generation.
And here is a site with audios of language which was spoken by Sorbian people born in 19-th century.
I don't know what theory Sokil adhere to, but as I think the old Rus founder Rurik stemmed from Polabian Slavs, especially Obodrites. The theory of Norwegian or Swedish origin of him seems for me unlikely. Why will Slavs ask a non-Slavic ruler to come? They couldn't even communicate with him, never mind share his values and religion. I suppose Ilmen Slavs to invite rather a very close to them Polabian Slavic Prince. You know, the Ilmen Slavs had very close relations with the Polabian Slavs. There is a theory, according to which the Ilmen Slavs are descendants of the Polabian Slavs.