Don't forget to factor in the cost of inflation. I know the airline business is very competitive but it's far enough away that you'll likely a % rise in airfare that's related to inflation and not just the Olympic premium.

The FTer in me says instead of saving for flights - use the money to speculatively take advantage of mileage promotions - I bet you could get enough miles through flying and miles purchase promotions between now and then to buy J airfare on JL / QF / NZ / NH / SQ / etc. (via any number of programs) even at a standard award level for less than the cost of buying it (and you may even get lucky and get a saver award if you're on top of booking the moment seats are released 331 days ahead of time)