So if I understand it correctly ALL currencies are converted into JPY with a conversion rate from the date that MtGox went offline. After the deadline for the Bankrupty Claims and after checking all the claims, the trustee calculates a percentage, based on the total available JPY and the total amount of all approved claims.

At an unkown date the trustee will payout the percentage based amount to all affected customers. This amount is in JPY also. If you want to be paid in a different currency, the amount of JPY is converted into that currency with the conversion rate FROM THAT MOMENT (the payout date).

Example
If I would like to be paid out in Bitcoin, an initial conversion rate of $483 is used (correct me if I'm wrong).
Let's say I've 25 Bitcoin and the calculated percentage will be 20%.

Total claim value in dollars: $483 * 25 BTC = $12.075

Payout 20% = $2.415
Conversion into Bitcoin based on initial rate ($483) = 5 BTC
Conversion into Bitcoin based on current rate ($230) = 10.5 BTC


In the future the trustee will ask us again in what curreny we would like to be paid out.
If the above example is correct, the final choice from everyone will depend alot on the Bitcoin conversion price (September 2015?).
If the (near future) Bitcoin price is to high then there is a risk that the trustee has to sell Bitcoins (market/auction)...

Another thing is that if the Bitcoin price will be $800 at the payout date, the trustee will have Bitcoins left in his wallet AFTER all the payouts are done.
On the other hand, if the Bitcoin price stays at the current rate, the trustee hasn't enough Bitcoins in his wallet to payout everyone.