i think Oneworld have to look for AirAsia (based on Kuala Lumpur (KUL), it's affinate is AirAsiaX, which is a long-haul airline based on KUL), to fill up the gap in South East Asia.
As:
1.MH is not so interested in Oneworld, although CX has code-sharing with MH for HKG-KUL route.
2.If MH joins *A or Skyteam, AirAsia will be the ONLY choice left for Oneworld to fill up the gap in South East Asia.