Anecdotally, it is spectacularly rising in value for me. Despite the fact that the meager percentage of the overall quantity of Bitcoin that I control is nearly fixed, the purchasing power of that Bitcoin has increased drastically. While that is skirting close to 'price' it is not the same thing. I can derive increasing value from it over time in the form of products and services.

And as near as I can tell, the number of Bitcoin holders is increasing over time. They are doubtless experiencing increasing economic capability due to their holdings of Bitcoin.

Increasing numbers of people deriving increasing economic ability is a multiplicative increase in value. For any reasonable definition of 'value'.

As an aside, until 2008, nobody was deriving any value from Bitcoin. That in itself disqualifies it from being 'unchanging in value', though I am willing to restrict the discussion to this step function. As long as the axiom is recognized and agreed.