Yes, I even heard that from one historian few years ago, borders of DDR aren't placed randomly.
Sorbs have been treated relatively fair in that country (comparing with nazi and earlier regimes).

Lusatian poet Jan Skala adresses to Serbs:

"My brothers in the south! Aren't there heart and soul that would see the North, Where in the German Sea
Small nation of Lusatian Serbs is struggling"…

Regarding the Croats, almost all modern researchers trace their primary location to Lesser Poland and partially to the north-east Czech Republic. Serbs lived to the west and north of the Croats, with the Czechs, Moravians and Slovaks to the south and the Poles to the east of them.