So what happens to my bitcoins?

Firstly, before any of the SegWit proposals activate, there will be no chain-split, meaning that there is only one Bitcoin. No matter which node you connect to, everyone is using the same Bitcoin. In TREZOR Beta Wallet, you might be using the “standard” Bitcoin wallet, but you will see the same balance in the BIP148 UASF Wallet.

Scenario: BIP91 activates.

Under this scenario, SegWit could activate on Bitcoin without the network splitting. However, there is a narrow window for it to activate, from July 21st to July 29th.

Scenario: BIP148 UASF activates, the network does not follow fully.

If BIP148 activates, but the network does not follow fully and the BIP148 does not become the longest chain, the Bitcoin network will split in two: BIP148 Bitcoin and Legacy Bitcoin. This is because BIP148 nodes will not recognize non-SegWit blocks, and thus will not accept Legacy Bitcoin’s blockchain as the longest chain. These Bitcoins will run in parallel.

Scenario: BIP148 UASF activates, becomes the longest chain.

If BIP148 activates and enough miners follow it, it might become the longest chain. By Bitcoin rules, the Legacy Bitcoin chain will be discarded and the network will follow the BIP148 chain. Bitcoin avoids a split, as all ready nodes should update to SegWit.

Scenario: SegWit2x activates, BIP148 does not follow.

As two different incompatible proposals go ahead with their intentions, the network is fractured and Bitcoin is split in two.

There might be a fork — chains might split into two different directions. However, the issue is that nobody knows if, how, and when it will happen.

TREZOR Users: Not Affected.

Luckily, if your bitcoins are protected with TREZOR, you do not need to worry about them. TREZOR is coin-agnostic — it is merely a signing device, and does not care with which blockchain it interacts. If the chain splits, we will do our best to support most, if not all of them. Then, the only thing that matters is to which node you connect your TREZOR.

If you are connected to a legacy node, you will continue using legacy Bitcoin. If you are connected to an UASF node, you will be interacting with BIP148 Bitcoins. If you are connected to a SegWit2x node, you will see SegWit2x Bitcoins. Moreover, you can switch between these nodes, like you can switch between other cryptocurrencies.

Of course, you can take precautions not to lose any coins. The important thing is that you should not send or receive any bitcoins during the times of uncertainty. Do not believe coin splitting services, or any too-good-to-be-true deals. They are often just scams, trying to steal your coins. In any case, as stated above, your coins will be split automatically, since you own the private keys to the original Bitcoin. If the network forks, so will your coins.

(The difference between this case and the hard fork case described in the linked article above is that in case of a hard fork, the date of the chain-split would be much clearer. Essentially though, all which is described in the linked article applies to this case too.)