Likely suicide at some point few years later. Ambitions are one thing. Capability to bring these ambitions to fruition is another. Manchukuo is kept nominally as a dependent state for several decades, and then given the independence separately from other parts of China. De-colonization was the major trend, regardless of the fortunes of the WWII.
I doubt that decolonization happens inside the Axis empires after an Axis victory without the collapse of those regimes as a whole.
Britain and France, despite having colonial empires, saw themselves as politically and economically liberal, and by the standards of what liberalism was at that time, they were. They had democratically elected governments, and they saw at least some value in the idea of self-determination, and had a press that could criticize the actions of the government.
Colonialism was an inherent contradiction with the liberal political systems of Britain and France, and decolonization was the obvious resolution to this contradiction.
On the other hand, Nazi Germany, and the Empire of Japan in the era of pre-1945 Shōwa statism, rejected the idea of political liberalism entirely. The philosophical/social background behind decolonization doesn't apply to the Axis powers.
In the case of the Empire of Japan during WW2, I don't see a way that they can turn back from their increasing militarization and nationalism, especially when military officers had difficulty even controlling the actions of their subordinates. If the Empire of Japan actually carves out a successful "Co-Prosperity Sphere", then they now have a bunch of vested military interests and economic interests in maintaining these colonies. They will only be forced out at gunpoint or if the Japanese themselves mass revolt against conscription making maintaining the territory untenable.
Of course it is unlikely that they actually conquer China in the first place and it would likely be a chaotic territory with communist guerrillas behind the lines everywhere. But if the conquest of China has somehow already happened, then I don't see how it's undone as long as the military dictatorship continues.