While there are any number of paths that the postwar German Empire could follow, I do not think that the empire would necessarily face a rapid and violent collapse.
The Germans, over time, will be faced with the demand for greater autonomy and independence from within the colonies. How the Germans respond to these kinds of developments would depend on the priorities and leadership of whichever government holds power in Berlin at any given time. The worst case scenario for the German Empire in sub-Saharan Africa could be something analogous to the conflicts that occurred in our world in Portuguese-ruled Angola and Mozambique, or in what ultimately became independent Zimbabwe.
In the end, I think that the overseas territories of the German Empire will gradually be transformed during the postwar years into something more resembling our world’s Commonwealth of Nations, albeit as a more centralized political arrangement. Although most of the empire would ultimately gain political independence from Germany, these new states would still have the Kaiser as their ceremonial head of state, and would likely continue to host German military bases, while German and Austro-Hungarian corporations would continue to have a substantial influence in the new countries. These high levels of post-independence German influence would, however, gradually fade as the independent countries themselves see the rise of new generations of nationalist leaders. The other great powers of the world will also seek to expand their own economic influence in the newly independent states at the expense of the Germans and Austro-Hungarians.
There are some overseas regions of the German Empire that could close to seek full political union with the empire itself, although I don’t think this would be a widespread postwar development.
