With that being said, it makes little financial sense for the miners to not be on board with this change. All else being equal, it will result in higher transaction fees for the miners.
When considering an individual block, then yes, replacing lower fee transactions for higher fee transactions makes financial sense and will maximize miner revenue. In the long term, however, full RBF will likely serve to reduce the overall fees paid by the community on the whole. If there is no concern about a transaction becoming "stuck", because every transaction can be replaced, then we will likely see fewer people broadcasting transactions at very high fees. They can simply instead broadcast at a much lower fee, confident in the knowledge they can bump the fee at any time if needed.
I am not sure if I agree with that logic.
full RBF will mean that every transaction is RBF. Not all transactions are such a low priority for the end user that a minimum fee can be used. If someone needs their transaction confirmed quickly, or within
x number of blocks, the transaction fee they will need to include will not change. Today, RBF is "opt-in", and that is true from a technical perspective, but from the end-user's perspective, it is really just a setting, and full RBF will 'require' this setting to be enabled. I don't think it really makes sense for someone to create a low-priority transaction that is not RBF today.
Further, most business which accept zero confirmation transactions only do so if those transactions pay a premium fee, one which is much higher than is necessary at the time. If full RBF ends the practice of zero confirmation transactions, then such high fee paying transactions will also disappear.
These businesses often effectively require customers to pay a next-block transaction fee. If a customer is willing to pay this high of a fee for ~instant acceptance by the business, they would presumably be willing to pay a similar fee for next-block acceptance.
Assuming that the average node defaults to 8 connections, then with only 10% of nodes running full RBF then each node has a 57.0% chance of connecting to at least one full RBF node. If 20% of nodes run full RBF, then that becomes a 83.2% chance. It certainly doesn't take a majority to run full RBF for miners to be relatively certain they will see any replacement transactions.
To extend this further, anyone can adjust the number of connections for their benefit. By default, if you allow incoming connections you can have up to 125 connections AFAIK (117 incoming, 8 outgoing). If a miner wants to be sure he'll listen to the double-spending, he can establish a connection with every node of the network (as long as it's bandwidth-wise possible of course).
I think projects like bitnodes.io do make use of this kind of network search tricks.
I would think that most miners probably use multiple nodes, most of which are not known to anyone outside of the entity that is responsible for broadcasting found blocks to the network. Otherwise, they would be at risk of sybil-like attacks.