In the not so distant future when the miners reward consists mainly of transaction fees, what is the incentive of a miner to forward received transactions to other miners?
To clarify, imagine you are a big miner (maybe a pool operator) and a transaction comes in from another node with a (considerable) fee. If you do not forward this transaction to the nodes you are connected to, you will reduce, admittedly by just a tiny amount, the chance that some other miner will include this transaction in the next block and reap those rewards if they find the block before you. By keeping it to yourself you can include the transaction in the next block that you will find.
If only one miner does this, the effects will be barely noticeable given the interconnectedness of the bitcoin nework, but if many miners have this behavior, could this potentially be a problem?