Is there potential that the 95% threshold could be reduced at some point?
Yes. Point.
Because 90% is also a majority. The majority *can* change anything in any consensus at any moment.
So if we reach 90% of segwit activation, we could vote that it's not 95% anymore but 90%? wouldn't that piss some people off? I don't get it so I would like to know.
Also, has a 95% of a big group of people ever agreed on doing anything? Shouldn't this have been foreseen a long time ago? I think 95% it's too much... but at the same time, it's great to guarantee that the big majority of people want something, but that 5% could be potential trolls, so I think 90% is probably a good enough compromise.