TPTB always have back-up legs in place to use as necessary; we just don't know what the original plans are, and what are the back-ups. (It's known, IIRC, that the visit to Phuket in one recent Race was a back-up plan, but we never knew what was originally planned, just that teams had to get to Bangkok in order to return to the planned route.) This time, these issues are coming up close to the end of the Race as its not clear what the options are. I doubt Russia will even be entertained, given international sanctions against the Russians over Ukraine, and western China won't happen because the Chinese will not let visitors into Tibet, and Sinkiang province is having a serious problem with Muslim insurgents. Beijing may be a alternative that fits the season one throwback theme, but that's hard to say one way or the other.
About the only option I can see is a diversion to Australia or New Zealand if that avoids the volcanic ash issue in Indonesia. Most of the other East Asia options will have weather issues for the next few days. And we know there are direct flights to the US and teams can connect if need be to reach the final destination city.
