Yes, most likely Japan and China would divide the rest of Asia between themselves.
Pan-Arabism, an example that I believe is closest to what we are trying to discuss here, worked because of several reasons that we need to understand here:
1. They had a unifying factor, other than the fact that they are all, well, "Asians". The Arabs were all on equal stance from the Maghreb to Mesopotamia, between the African and Gulf Arabs - believers in the Islam faith, speakers of a non-dialectic Arabic, etc. If Asia is to pursue something that looks similar to what occurred in the Arab world, it is possible the movement may be quite limited(the Sinosphere).
2. They all were in equal standing, more or less; or, more to say, there were multiple major players. After the fall of the Ottoman Empire and colonisation of those regions by Europe, all nations were cut up into similar pieces and did not have complete supremacy over one another. This is not the case for the Sinosphere - unless, of course, China falls completely and the warlords declare independence.
3. Most of them were directly colonised. This meant that, unlike the Sinosphere, the nations were all resisting European powers and thus unified them against the common enemy, along with bringing them to a more desperate position(necessitating a unified front). In the Sinosphere, only the Philippines and Vietnam are colonised by Western powers(counting the Philippines into the Sinosphere).
There are much more that we can go into if we pursue detail, but the general point is clear: we need elements both from outside and within which brings a group of nations together. For that to happen, Asia(by differing definitions) can either be too large a nation-group to see a unifying factor, or can be too dominated by large, previously imperialist nations. And it will be especially hard for the Sinosphere because it was historically dominated by the Confucian domination-tributary system; as I said, only with a shattered China(and, I should add, a not-very-strong Japan) can we forsee the true development of Pan-Asianism.