Maybe the Freebitcoin team will also reduce all prize amounts to be smaller if indeed bitcoin is worth $ 500k and we don't know what they will do if that happens but I'm sure the Freebitcoin team already has and prepared a big plan for Bitcoin when it's in that price.
The rewards from the freeroll will adjust automatically to the movement of the Bitcoin price when it goes up or down, but if the bitcoin price reaches $ 500k then the lowest value that will be obtained from the freeroll is still 1 Satoshi because that is the lowest value in Bitcoin units, or they can also change fractions Bitcoins to µBTC.
Yes, that's true because if you don't follow the bitcoin price and when Bitcoin reaches $ 500k, the RP value is not changed, then Freebitcoin will suffer a loss.
Maybe for prizes if the amount is not reduced then Freebitcoin will definitely provide more difficult terms and conditions for users to be able to take prizes that have been given by Freebitcoin through several games.
To replace Bitcoin with uBTC it seems that Freebitcoin will not do it because in terms of value it is already very different and Freebitcoin is a platform used by gamblers to hunt for Bitcoin so if it is replaced with uBTC I feel the users in it will be a little disappointed.