There will be no replay protection, and even if there were it would make no difference.
Why? Because Bitcoin and Segwit2X cannot both survive.
I used to think that both coins would survive and that both communities would divorce and live happily ever after.
The problem is that both coins share the same PoW algorithm.
If both coins survive the hashing power will fluctuate dramatically from one coin to the other depending on short term price fluctuations, making both coins unusable. We'll have periods where Segwit2X works and Bitcoin doesn't, and periods where Bitcoin works and Segwit2X doesn't. The situation is untenable on the long-term.
The only reason why Bitcoin cash is able to survive the extreme hashrate volatility is because of EDA, which Bitcoin and S2X do not implement. Bitcoin and S2X will not, cannot both survive. This is why S2X will not implement replay protection: because either it manages to kill Bitcoin quickly, or Bitcoin will kill S2X. If this does not qualify as an attack, I don't know what does.
The mutual exclusivity of the S1X and S2X branches presents the most powerful validation of miner honesty that Bitcoin has enjoyed in quite some time. Miners have clearly signaled their intention to modify a network rule that affects how they achieve concensus. Since their value to the network is their ability to determine the validity of a single history among a set of mutual exclusive options, they cannot signal for NYA/S2X then subsequently extend the S1X branch and remain honest.
It is up to the rest of the Bitcoin system to reject the proof of work generated by a network of provably dishonest nodes. If the hash power fluctuates between logically inconsistent histories, the hash power used to signal the rule change has been proven dishonest. The design of Bitcoin is resistant to some attacks by a hostile mining majority, but that is no reason to continue supporting the work of a dishonest network.
The way you provide the facts are biased.
The current list of companies on bitcoin.org aren't endorsing 2X in it's current state. They signed it under the impression that it would avoid a chain split, and that miners would act honestly.
Bitmain did the opposite, acted dishonestly, and caused a split the NYA signers aimed to avoid, which voided the entire agreement...again, an agreement that still was never backed by the community at large to begin with.
Many of these signers have not spoken up since that incident (including Coinbase) and can not be considered to currently support the 2X chain.
Silence is not support. The social contract they agreed to has been made void.
So like you said:
"List shows companies who have not endorsed but not necessarily opposed to it."
Likewise: That list of companies still on the NYA list on bitcoin.org agreed to something much different than the current environment and the fact that they haven't publicly renounced their agreement does not necessarily indicate they still endorse 2X, or ever did.
Many came straight out and said they only agreed to it thinking it would prevent a chain split, and that the developers and community were behind it. This agreement was shot down on day one by everyone here.
These are facts.
I don't need to refute what you said, I simply need to counter it with the same method you use and let the people decide.