What makes you think that people are going to dump their *original bitcoins* to buy the new altcoin, and they didn't do that with the existing litecoin ?
The very same thing which makes Ver&WU to think that people gonna name their alt as "bitcoin".
That's for people to decide and we will never know unless it happens and trust me it will happen. There will be many forms of bitcoin and only one of them will bear the "bitcoin" name.
In fact, Ver and Wu's coin have more chance to ever be called "bitcoin", because the *actual bitcoin miners might decide to give up on the original, and switch to the new one, abandoning the original one and lowering its hash rate*. However, with a PoW changing HF,
all the current bitcoin miners will continue to mine bitcoin, with the same hash rate. Because that's all they can do with their hardware !
It would BTW be funny to see the new bitcoin and the amount of PoW that goes with it. Bitcoin has been marketeered as super more valuable because it had the most PoW and was the safest chain (this is somewhat bullshit, but it is part of the bitcoin dogma's and one of the reasons why bitcoiners think bitcoin is for ever superior to any other crypto currency). If you invent a totally new PoW scheme, of course, in the beginning, there won't be much proof of work as compared to the original one ! If it is a GPU based algorithm, chances are that it will be largely inferior in cryptographic security than the original chain. How to convince people to leave behind "the most secure chain ever", to jump to some totally new thing that could be 51% attacked at any moment (for instance, by ETH miners). What if someone (bitmain) has actually an army of ASICS that haven't seen the market and takes over all the hash rate ?
When Asics took over from GPU and FPGA in bitcoin's history, the chain wasn't worth as much as today, and code was centralized on Core. Can you imagine the impact if there's essentially a hardware monopolist that fully takes over the new chain ?
In fact, you could do such a fork, and "true bitcoin" might not even be aware of it ! There's strictly no reason to suddenly start naming the original bitcoin, which happily continues to function, something else, because someone forked off an alt coin. Ethereum was different, because the Ethereum Foundation has its name in a way, and because ethereum didn't change PoW, the original ethereum miners that were mining the original chain (ETC) abandoned largely the original ethereum (ETC) to go to the new one. Nobody thought that the original ETC would continue to exist, but it did.
With bitcoin, that will not be the case, because *all* bitcoin miners will continue mining bitcoin like before. The chain will not stop because someone decided to make a different coin.
But all this is theory. I would like to see the UASF with a change in PoW pulled off and watch what will happen. I think I know what will happen, but it is always better to do the experimental test.