(These threads exist so figure I may as well help get 'em going.)
So, I was thinking about this somewhat and (while I know some stuff has apparently been locked down I'd assume there's still room for input on the general specifics of how things came about) some stuff I've sort of put down for APC's history so far is that it formed following the ratification by all states of the Treaty of Taipei in 2061; then before that we presumably saw from 2015-2025 the climax of tensions over the South China Sea as well as over Taiwan; probably by 2030 we see regional powers, with pressure from ASEAN and no doubt powers outside the region (US, etc.), begin to really invest in peace and probably by 2040 the South China Sea will have been figured out, an agreement could be in the works or already finalized for an independent Taiwan, and the Korean War could finally be brought to an end.
From there we no doubt have more regional organizations popping up, the formal establishment of diplomatic ties between China and Taiwan and between the two Korea's, and by 2045 the role of ASEAN will have grown so large in Asia-Pacific politics as to officially reform as something like the Association of Asia-Pacific Nations (AASPAN ?).
By 2050 at the latest the southern Pacific (Australia, etc.) will of been brought into the mix in an effort by those governments to advance their economic, political, and security interests and as such by 2060 the developing political and economic institutions now spanning across Asia and the Pacific will have reached sufficient maturity as to warrant taking seriously talk of unification.