However, we know that replace-by-fee (RBF) transactions are possible.
Replace-by-fee transactions are opt-in, you have to specifically make transaction with this flag for it to work. Regular transactions can't be easily replaced, today's nodes are configured to ignore new transactions that conflict the one's that are already in their mempool. So, the answer is, either a miner would mine it for themselves, or the fastest sender will take it. Tx fee will be higher than average, but nothing too crazy.
The most likely outcome is that miners will take it for themselves and pay no transaction fee. Which miner/pool gets the additional reward is a matter of hash rate.
I doubt it's likely, there's only ~10 minutes timeframe to do it, and the person who does it can't be just a regular miner, they have to be the administrator of a mining pool, and they have to quickly reassemble the block they want to mine, and then win the race against the network. And for miners this transaction looks like any other transaction, so they can't automatically detect it on their side.