Bitcoin was originally created to be an anonymous currency
That was never one of the core aims. Read through the whitepaper.
I don't think the price of bitcoin will decrease anytime soon because we are still at the beginning of the curve of adoption
This is assuming that everything which rises dramatically in price must continue rising until there is literally no money left that could
possibly fuel it.
What you're missing is that a significant amount of people will continue to be skeptical or uninterested, and some people will be scared away, considering it more likely to be a bubble if the price rises higher. If we went by your logic, pretty much everything would be worth
loads.
It looks like a Ponzi scheme because, when every potential bitcoin users of the population will have exhausted all of their "potential of speculation", there will be nothing left to sustain the price of the bitcoin.
A Ponzi scheme involves a central authority gaining money by accepting investments into a central platform and then distributing money to earlier investors. A speculative asset and a Ponzi scheme are entirely different, and it would be ridiculous to conflate the two terms.