It were the Magyars who hgave the Karantanian marches the final death blow, wasnt it? Though they had degenrated before already... Still, those were German marches, and like in the East Elbian lands they would most likely steadily have been expanded over at least West Pannonia, with some luck on their part over all of Pannonia - including, as in teh East Elbian lands, German settlement. Just that yes, those settlers would be Bavarian instead of Saxon and Thuringian in the East Elbian lands...
Maybe Great Moravia can win East Pannonia, maybe not (I dont think tehy could attack Bavaria directly to gain West Pannonian lands). Or maybe also the Avars make a comeback and retain East Pannonia. Or as said it also becomes German, or its split between Avars and Moravians... lots of possibilities...