There are way many bitcoins at stake that are pro-1MB legacy chain that those who are willing to sacrifice their 1MB legacy coins for segwit2x chain coins. Just take a look at the bets on twitter. Gmaxwell, Adam Back, Trace Mayer and so on, were talking about making bets as high as 25,000 BTC. Roger Ver was too scared to take it.
While I commend their willingness to put skin in the game, I don't think any of that is meaningful. 25,000 BTC may look like a lot to plebs like us, but it could easily be absorbed by the OTC or exchange markets. It's a drop in the bucket. Like someone said up-thread, the diehard #No2x crowd is louder and likely holds more coins than diehard #2x supporters. But I think they are both just loud minorities anyway. What matters is
the meat of the ecosystem, and I wish I knew of good metrics to analyze just how economically relevant the NYA companies are.
In any case, I don't think that Coinbase, Gemini, Bitpay, Blockchain, Xapo, Shapeshift and the other NYA signers are economically irrelevant. If they are calling a different network "Bitcoin" and moving their economic activity to that network, that is significant value leaving Bitcoin. We could be talking about amounts of money that make 25,000 BTC bets look silly.
About Coinbase users, they can easily lawsuit them no matter how many "terms of conditions" Coinbase comes up. That will waste resources on them.
There are no legal precedents here. I suspect that Coinbase has very competent legal counsel, and that as long as they provide their customers with both coins and ample opportunity to make use of both coins, that there will be no grounds for lawsuits.