I'll have to write a guide about this at some point.
The btc.com online wallet claims that they will support coin splitting. Since they are also a mining pool, it seems likely. I have placed a very small amount (it is an online wallet, after all) with them, that I expect to use to taint and split coins, if we get two viable chains.
But I think it is far from sure there will be a true fork. The plan of the 2x guys is a crushing victory. They expect (or hope for) getting the vast majority of the hashing power, in which case at least some exchanges may declare the 2x fork for the real bitcoin. In that scenario, I expect the community to move to the 2x chain, some will think bitcoin has been upgraded, other that it was downgraded. Then chain split is likely, as it seems that the strongest 2x opponents will continue with the old chain.
Anything else than this will be a failure for the 2x guys. That can happen in many way.
1. It is all a bluff, the split never happens (extremely unlikely, imo).
2. The 2x chain splits off, but with a minority hash rate. In that case 2x coins will be a low-value altcoin, and the lack of replay protection which is intended to kill the minority chain will backfire badly, and make it very unattractive to work with. In any case, I do not think the NYA miners are interested in mining a minority alt-coin, so I am not sure anyone will have the time to move and sell their 2x coins before it dies. The hard-core large-blockers will probably find it more attractive to move over to BCH, some of them are religiously against segwit anyway.
3. The 2x chain gets a majority, but not a crushing one. In that case I doubt any exchange will risk calling it the true bitcoin, and I suspect it will have much lower value than the original chain. Again I think miners will abandon it.
So only in case of a crushing victory to the 2x side is a true chainsplit likely in my opinion. But in reality I have no clue what will happen. It is impossible to judge what people think or discuss it properly. /r/bitcoin censors any post that is attempting to discuss a block size increase or is not clearly against 2x. /r/btc is patrolled by trolls that downvote any post that does not seem to imply that the core developers are evil people controlled by the Bilderberg group and/or space lizards. No sane discussion is possible.
