If the community is behind it, then a POW change would render the 10s/hundreds of millions of dollars in mining equipment worthless.
So the real question is whether or not the UASF side has the support of the community or economic majority.
You change the proof of work algorithm so that the existing miners can't use their fancy Bitcoin miners, and it becomes profitable to mine with GPUs instead.
Peercoin is one of the first working proof of stake implementations that has been running for close to 5 years now.
If the community is behind it, then a POW change would render the 10s/hundreds of millions of dollars in mining equipment worthless.
So the real question is whether or not the UASF side has the support of the community or economic majority.