Even if UASF will create altcoin then be it.
.....
I will use BTC as store of value and UASF to play casinos, pay for stuff. Same time let original BTC be original BTC.
You don't have a clue. UASF won't split it's a softfork. Some stupid miners like jihad and BTU bovine can ragequit and create their altcoin BTU, but it will be just alt like LTC, no more
What non-mining nodes do with a UASF doesn't matter of course. As long as the miners continue mining one chain, UASF nodes will stop, because they will find, on the only chain out there, blocks that are not valid (non-segwit signalling blocks).
So as long as miners are making a chain like they do today, the only thing you obtain with a UASF non-mining node is one that stops. You could just as well switch it off.
However, if
a minority of miners is actually eager to split off with segwit, then they could take this as a signal to start making a minority chain. Note that they could do so already. The only thing that is needed is that users wanting to use this fork of the chain, should connect their wallets ONLY to these mining pools, that keep the short segwit chain ; if ever they also connect to another node, their wallet would find a longer chain (the non-segwit chain), and discard the shorter segwit chain. But if
1) you configure your wallet / full node to ONLY connect to segwit signalling mining pools
2) segwit signalling mining pools have decided to fork off with a minority chain <--- this is essential
then you get the same effect as using, as a user, a UASF node or wallet. The only thing that a UASF wallet or full node does, is to reject non-segwit blocks, and hence, it would automatically refuse the majority chain ; you wouldn't need to force the connecting partners, it would refuse all other nodes unless they have a copy of the segwit-only minority chain out there.
Note that as long as miners don't decide to make a fork, and go on a segwit-only minority chain, next to the majority chain, nothing will happen, and UASF nodes will simply stop.
BUT, but:
This is a very risky situation, for both forks. If both coins are now listed in the market, on exchanges, that is: BTC-original and BTC-segwit, then we are in a kind of similar situation as with the ETC/ETH split, but this time, the BTC-segwit fork may very well win in the market. Miners will follow the relative market caps.
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if now, the segwit minority chain becomes majority, it will become the longest chain. And because segwit is a SOFT fork, it would now simply ORPHAN the non-segwit chain which was initially majority. This is the difference with the ETC/ETH split, which was a hard fork.
For this to happen:
1) exchanges need to list the two bitcoins
2) users in the market need to prefer the segwit bitcoin over the original bitcoin and vote with their money, selling their original bitcoins, and buying segwit bitcoins in majority
Miners will follow with their hash rate.
Whenever the segwit chain overtakes the original chain, the original fork becomes orphaned (can be a month later) and all the transactions on it disappear in a puff.
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However, it can also be that the segwit minority fork doesn't get traction. With the slow difficulty adjustment in bitcoin, the segwit chain will make blocks at a much smaller rate (minority) than the non-segwit chain. If, say, segwit has 30% of miner hash rate, it will make only a block every 1/2 hour. This will make it very difficult to transact on it. It may very well be that transacting on it is such a pain, that people prefer to stay on the old chain, simply because they cannot transact on the new chain, it is too slow. You may say that segwit will have 4 MB of transaction volume, but that is not true. It has only 1 MB of transaction volume for "old style" bitcoins. It is only when you did an old transaction to a new segwit address, that you may, AFTERWARDS, transact in the 4 MB volume.
So if ever the segwit minority chain remains minority and/or dies off, then all segwit transaction coins disappear in the same kind of puff. After all, with the slow bitcoin adjustment times (2000 blocks), if you have a 30% hash rate split off, you will only get your next difficulty adjustment after 6 weeks, so during six weeks, you make blocks at a half-an-hour rate.
For miners, it is in any case risky to fork off separately, if both coins are listed on exchanges, and the market cap splits. The reason is that during the time until next adjustment, you have to mine at the same rate as before, to get only the reward (in $) of one of the branches. For instance, if BTC is, say $3000 at the moment of forking, and in the market, the market cap splits 50-50, so that a segwit bitcoin is $1500 and an original bitcoin is $1500, you will mine as many coins as before on your choice of fork, but they will bring in only $1500 instead of $3000 if you sell them.
For users, it is maybe unwise to sell one of their type of coins in the market, because of the fact that it is a soft fork, their branch may disappear and they may lose everything. The segwit forkers may abandon if they stay minority ; the original chain may be orphaned after a month or so if it becomes minority.
This would lead to a kind of permanent market split in ratios of about 50% - 50% if users want to keep the two options, doing everything in parallel on both forks.Note that I only considered the segwit fork to be minority.
If segwit is majority from the start, there is NO NEED FOR UASF. The segwit splitters can impose their majority hash rate on the original chain directly. Whoever is still minority hash rate on the original protocol, will get orphaned all the time. So if ever segwit becomes majority (50%), they can fork off, and force the whole chain.... if they stay majority !
However, if ever they lose majority, the original chain will go on, and we get a clusterfuck of mixed segwit blocks and non-segwit blocks.So in any case this will be an adventure full of suspense, in which the users starting UASF don't matter much apart from the psychological effects. It will be the miners that have to decide to fork off, and the market that will decide in a risky game.
