A quick braindump on what might happen in case SegWit2X proponents don’t back out.

Breadwallet, Jaxx, Electrum?, GreenBits, Airbitz, “Simple Bitcoin Wallet”, “Bitcoin Wallet”, Multibit, Bither, HiddenWallet, BreezeWallet

Backgroung

SPV wallets adds up 50% of the Bitcoin ecosystem (number pulled out of my ass).

SPV wallets connect to full nodes and sync longest chain headers, be the blocks any size.

According to Coin.Dance there are approximately 7,000 Bitcoin nodes and 200 SW2X nodes. These are listening nodes only, but this all that matters.

It is suspected SW2X will have majority hash power, but no community support. So the question is:

In the event of a hard fork how SPV wallets will behave?

First I’ll assume SPV wallets are not prepared for SW2X chaos. It is a fair assumption, because even if they release a version that ensures their nodes stay on Bitcoin, people won’t update that fast.

Next I’ll assume SPV wallets are written properly and handle huge orphanings perfectly. This is not a fair assumption, it is possible that many SPV wallets will just crap itself together, but let’s say they don’t.

In this case, since there are so few SW2X nodes, they will not see that chain for long (months), until they accidentally find an SW2X node and reorg themselves, because their chain will be longer.

An other problem is, if they lose their SW2X connection and the Bitcoin chain grows to be higher than the last known SW2X chain, then another huge reorg happens, until the next huge reorg when it finds another SW2X node accidentally.

Conclusion

We’re fucked.