If the Magyar fail to hold the Pannonian early on it will likely go the same way as Wendland did. It will be settled by Germans, in this case (Austro-)Bavarians. This will make Slovakia more likely to get the influx of Germans from Silesia slightly earlier. The result will be the areas of modern Hungary and Slovakia will be majority German when we enter the early medieval period. It will likely make little difference in Bohemia before the rise of nationalism.