Are you talking about the territories roughly corresponding to Baden-Württemberg, or literally Baden-Württemberg?
If the former:
Charles the Bold of Burgundy refuses Sigismund of Tyrol's offer of mortgaging the Habsburg Vorlande in 1469. Tyrol keeps losing wars against the Swiss, and are eventually forced to cede the Sundgau and Breisgau to the Swiss or face bankruptcy. The Swiss expand throughout these territories, and eventually end up in conflict with Baden and/or Württemberg. Swiss victories in these conflicts lead to the eventual annexation of most or all of their territories. (This dominance in Swabia beyond the Vorlande would be unlikely to last though)
If the latter:
Unlikely to the point of being ASB, given that Baden-Württemberg didn't exist until the 1950s